Hemospectrum

The Hemospectrum is the spectrum of blood colors possessed by trolls, which forms part of their caste system, with social and biological implications. The blood of a lusus appears to be the same color as its associated troll, implying that it is a large factor in the selection of a lusus. Andrew Hussie has confirmed that there are only twelve possible troll blood colors, excluding mutations.

The cherubs possess different blood colors as well. However, it seems that their system is binary instead of a spectrum, with the color indicating a cherub's moral alignment – green for benevolent and red for malevolent.

Social Aspects
There is a caste system on Alternia based on the color of an individual's blood. The hierarchy follows a rainbow, with red being the lowest and purple being the highest. There are several terms covering chunks of the hemospectrum. Aradia refers to Tavros and herself (the two being the lowest on the hemospectrum) as "rust bloods," while Terezi, Vriska and Equius have all been referred to as "blue bloods." Lowbloods is used to refer to the lower half of the spectrum and highbloods is used to refer to the upper half of the spectrum. Midbloods is used, rarely, to refer to olive to cerulean bloods, with the castes within it usually referred to as lowbloods or highbloods depending on their position in the spectrum.

Higher blood castes seem to have more lavish hives: both Equius' and Vriska's hives resemble castles as opposed to Aradia's humble hive. Both Eridan and Feferi wear jewelry as well.

When asked by Terezi what color his blood is, Karkat gets defensive; although the other trolls hemotype, Karkat masks his in anonymity by using a gray tone. When Karkat arrives in the Land of Pulse and Haze, he appears to be surrounded by a river of red, which he believes to be comprised of his own red blood, a mutation that places him outside the "hemospectrum." It has yet to be revealed what significance this has, but his ancestor suffered from the same mutation.

Initially some of the trolls believed human blood works on a similar system, although only Equius, Eridan and a sobered Gamzee seem to care much about the hemospectrum. Terezi is also very curious about human blood, specifically about how it tastes and smells.

It is possible that the blood-color caste system may correspond with medieval class systems on Earth. Based on this supposition, purple blood would be high royalty, blue would be nobility of sorts, green would probably be lesser nobility, and red would be peasantry. The intermediary colors are harder to discern but may correspond to other roles in feudal society or may fall under the previously listed four groups.

On Beforus the hemospectrum was used to set up a system of social welfare in which the higher blooded trolls take care of the lower blooded trolls. The system is one of receding responsibility. The fuchsia bloods (the queen and her heiress) are responsible for the well-being of all her subjects, while burgundy bloods are free from any duties to take care of other trolls.

Hemotyping
Hemotyping is a tradition in troll society and potentially amongst cherubs where a person uses their blood color for writing and as the color of their symbol. While most of the trolls practice hemotyping, Karkat, due to his mutant blood color, refuses to partake in hemotyping, which causes Vriska to refer to Karkat's text as HS 4196 ("".) Calliope and Caliborn both renounced hemotyping HS 6862 (as one of the rules in their game); however, their symbols retain their respective blood colors as well as their gray text colors.

Out of the trolls that do practice hemotyping, a number of them use a different shade for their text as opposed to their exact blood color; specifically, half of the Alternian trolls use a different shade, namely Tavros, Kanaya, Vriska, Equius, Gamzee and Feferi. The reason(s) behind this are unknown. Despite this they use the shade of their blood color for their symbols as opposed to their text color.

Biological Aspects
Blood color seems to have several biological consequences in addition to the social consequences of the caste system. Troll tears are apparently the same color as their blood, though more diluted in color. Trolls lower on the hemospectrum are more likely to have psychic powers, but are more psychically susceptible as a result. On the other hand, trolls higher on the hemospectrum seem to be more physically strong. Another obvious aspect is the different anatomy of land- and sea-dwelling trolls. The latter sport fin-like protrusions and organs that allow them to live underwater.

Equius remarks that Gamzee has the highest blood possible for a landdweller and is as such more prone to violence and murder than the rest of them. Equius also states that he dreads to think what he would be without the pacifying influence of his moirail, Nepeta. This implies that trolls gradually become more psychopathic/violent the higher they are on the hemospectrum. This would mostly be in line with the twelve trolls followed in Hivebent, as the trolls below Terezi on the spectrum are fairly "harmless", while from there onwards the trolls display some unnerving behaviour peaking in Eridan's outright genocidal tendencies. The only true exception seems to be Feferi, who, despite being at the very top of the hemospectrum, displays no negative tendencies, although she might only be suppressing them by force of will, since she was screaming while attacking an imp HS 4478 (here). On a possibly related note, Aradia starts displaying more violent behaviour after entering her blue blood-fueled Soulbot.

In a dream bubble conversation Terezi has with Aranea, who was masquerading as Vriska at the time, it was implied that high-blooded trolls are tougher than low-blooded trolls and likelier to survive grievous injuries. In the same conversation, Aranea states that the trolls' violent behavior is a result of 's conditioning of their race, implying that the high-blooded trolls may not be as unstable as was previously thought.

A troll's lifespan is also tied to the hemospectrum with the having lifespans similar to humans, with the lowest two being slightly shorter than humans with the lowest caste living for HS 5968 (a dozen, or a couple dozen, sweeps) (roughly 30 to 50 years in human terms). Starting at the greens, lifespan and by the highest caste lifespans reach hundreds of millennia, potentially even millions. Mindfang, a cerulean blood, wrote in her journal that she expected to live for centuries and predicted the Summoner (Tavros' ancestor), who was destined to kill her, may very well not hatch for many sweeps, given the shorter lifespan granted by his lower position on the hemospectrum. Kankri stated in Openbound that cerulean bloods with their centuries long lifespans could outlive hundreds of generations of burgundy, bronze, yellow and lime bloods, and dozens of generations of midbloods.

Some castes have uneven sex ratios. For example jadebloods are almost entirely female, the three blueblood castes (cerulean, indigo and purple) are mostly male, and fuchsia bloods have been consistently referred to as female (empress, heiress etc.).

Candy Red Blood
Candy Red Blood is an extremely rare mutation on Alternia. Karkat Vantas, his ancestor the Signless/Sufferer and his pre-scratch counterpart, Kankri Vantas, are the only trolls known to have this blood color. Karkat and his ancestor fear/faced ostracism based on their mutation. Due to its rarity, there was no lusus in the Sufferer's time that would choose him and the Dolorosa raised him herself; Karkat was only afforded a lusus due to the actions of the followers of the Sufferer, who prepared for the birth of another candy red blooded troll due to the prophecies told by the Sufferer. It has also been called "bright cherry blood" by Calliope and Terezi, the latter of whom associates its "smell" with cherries.

The abilities inherent to candy red blooded trolls are not shown. Unlike other lowbloods, Karkat is never seen exhibiting psychic powers. However, he is shown to have a great knowledge of the way the quadrants work, and both he and the Sufferer have managed to form bonds that exist outside of the four known quadrants. Both have also managed to unite trolls of different blood colors against a common threat.

This blood color is also known to exist in cherubs and is possessed by Caliborn/. This color sets them as the malevolent mind in their body.

Burgundy Blood
Burgundy Blood is the lowest blood caste in existence. Kankri referred to the color as "burgundy" in Openbound. Rust has been used on a music album, but in the comic rust was used to simultaneously refer to Aradia and Tavros. Burgundy bloods are notable for having the shortest lifespans - having stated that they generally live only a dozen sweeps or two, or roughly 30-60 human years. They are the most likely to have psychic powers. This is a double-edged sword, however, as they are also the most psychically susceptible, and would be the first to die in the event of the Vast Glub. Despite this apparent vulnerability, Vriska is unable to use her powers to control AradiaHS 4145.

Aradia Megido's psychic powers allow her to manipulate the position and velocity of objects. The Handmaid is also known to have such telekinetic abilities, though she was only seen exhibiting them as a child. Using her tiara, the Condesce was able to emulate burgundy blood telekinesis, displaying Aradia's symbol and the same white auraHS 6773. Her pre-scratch counterpart Damara Megido was able to HS 8461 (lift the Prospitian battleship) on LOMAX, through the concerted efforts of at least three of them at once, all the way from a dream bubble.

Aradia also possesses the ability to summon ghosts, commune with them and command them to do her bidding. After her death, she continued to linger on Alternia as a ghost, using her psychic abilities to interact with her surroundings. No other trolls have displayed similar abilities.

Working together, the army of Aradiabots were able to HS 4492 (protect the other trolls) from the Black King's Vast Glubs.

In Hiveswap, there are at least two burgundy-blooded trolls, Xefros as well as a tall skinny one with spiral horns, overalls and a shovel.

Bronze Blood
Bronze / Umber Blood is the second-lowest class of blood. They are more psychically susceptible than most trolls as well, but again said to be more likely to develop psychic powers. Trolls of this caste have also been called fudgebloods, and Terezi associates the blood's smell with chocolate. This was referred to as Bronze in both the music album and Gamzee's potion. Kankri refers to this blood caste as Umber, however the term has never been used by post-scratch/Alternian trolls, and may be exclusive to Beforus.

Tavros Nitram and his ancestor the Summoner have the psychic ability to commune with and command the various beasts of Alternia (and in Tavros's case the Underlings of the Incipisphere, possibly due to their Lusus prototypings). It is not stated if Rufioh Nitram also shared in this affinity with animals, although both he and Tavros are avid players of Fiduspawn in which Tavros uses his abilities to commune with the game constructs.

Troll Kevin James has bronze bloodHS 4304, as do some or all cavalreapersHS 4016‎HS 5658‎.

In Hiveswap, the unnamed antlered troll is an example of a bronze blooded troll.

Yellow Blood
Yellow / Ochre / Gold Blood is the third-lowest blood color. They are also very likely to have psychic powers. "Gold" is the color used in Gamzee and Jane's potion shop for a vial of Sollux's blood.

Sollux Captor, his ancestor the Ψiioniic/Helmsman, and his dancestor Mituna Captor are all powerful psionics, with Sollux and the Helmsman capable of using their mental powers to move massive objects at high speed; the Helmsman himself was used to power the Condesce's own battleship, making it the fastest out of all ships in her fleet. Sollux is also capable of firing destructive blasts from his eyes, and the Condesce displayed the same ability while emulating yellow blood psionic powers. Sollux used his powers to make the bees from his beehouse mainframes sleepHS 3980 (which might be related to his ability to interfere with computer equipmentHS 4411), but he cannot read mindsHS 3927. Sollux and Mituna are both gifted with "vision twofold", but this may merely be a trait unique to the paradox clones (possibly related to their shared Aspect). It should be noted that "vision twofold" is simply a reference to how Sollux still possessed his vision while having the ability to see the future (specifically, future deaths) unlike the traditional imagery of prophets being blind. In addition, both Sollux and the Ψiioniic/Helmsman die due to the Vast Glub released by Gl'bgolyb while they are directly serving their fuchsia blooded companions; in comparison, Mituna dies at the hands of Meenah's use of the Tumor.

In the era of the Signless, psychically gifted yellow bloods were commonly enslaved as HS 5958 (mages) or HS 5960 (helmsmen).

In Hiveswap, the beekeeper troll is implied to be a yellow blood by the prefix on their 2D image.

Lime Blood
Lime Blood was a very common blood caste on Alternia but was hunted to extinction by the others due to its members' possession of powerful abilities that threatened the authority. Calliope has stated that the lime bloods had some unusual names. Kankri Vantas refers to members of the caste as "yellowgreens", considering the term "lime blood" offensive due to its historical connotations, implying that the caste was historically oppressed on Beforus.

The lime blood color was originally alluded to when the Grand Highblood was introduced, as there was a shade of green previously unaccounted for. The existence of the color was later confirmed by Hussie, and HS 5414 (the page) was retroactively changed to feature a lighter shade of green. This lighter shade fits in the color wheel between Sollux's yellow and Nepeta's green, where Karkat sits when the group is arranged by the procession of their zodiac symbols, suggesting that he (and, by association, the Sufferer/Signless) would be a lime blood if not for the cherry red blood mutation.

Calliope has stated that she is a lime blood, and proceeded to elaborate on the lime blood caste of trolls; however, at that point nothing more was said on the hemospectrum of cherubs. When asked if she had the powers that lime blooded trolls have, she answered, "" However, whether or not she has lime blood powers is largely irrelevant, since she is a cherub and not a troll. Calliope being a lime blood may also relate to how she uses Commonwealth spellings, as an old derogatory slang for the British is "limey". The color of lime blood amongst the cherubs is drastically different from that of the trolls, and looks similar to the web color harlequin. Slight variations of this color are used in Calliope's caudeceus/asklepion symbol, in the colors associated with the depiction of Calmasis. Caliborn refers to her blood as "harlequin slime".

Olive Blood
Olive Blood is considered the "middle class", and the color is referred to as "ok but not great" by Equius. Equius and Nepeta simply call it "green", but this may not be the specific term, as there are two other shades of green on the hemospectrum. "Olive" has been used to describe a potion of the same color, which was HS 8300 (strongly implied) to be Nepeta's blood.

Nepeta Leijon, her ancestor the Disciple, and her dancestor Meulin Leijon are not known to have any sort of psychic power. This may indicate that somewhere in the green part of the hemospectrum, trolls start to be more likely to be born without psychic powers. This is also the blood color of Troll Will Smith's character on Thresh Prince of Bel-Air, and possibly Troll Will Smith himself. The threshecutioners included olive bloods within their ranks (as well as HS 3908 (bluebloods) of unspecified hue).

The gatherer from Hiveswap also appears to have olive blood.

Jade Blood
Jade Blood is rare among trolls, and trolls with this blood color are given a unique role in troll society. In the past, jade blooded auxiliatrices were tasked to tend to the Mother Grubs in the brooding caverns. On Beforus, they were a predominantly female caste and their duties also included caring for wigglers.

Kanaya Maryam, her ancestor the Dolorosa, and the latter's pre-scratch self Porrim Maryam are the only jade blooded trolls described in Homestuck. All of them seem to be able to withstand the intense light given off by Alternia's sun. Kanaya, who is afforded the privilege of being brought up by a Virgin Mother Grub ("HS 4223 (an event so rare as to elude documented precedent)"), also eventually turns into a rainbow drinker (the Alternian equivalent of a vampire who can withstand sunlight and radiates light) upon her death at the hands of Eridan. Porrim became a rainbow drinker as well, even before their session began. It is not known if the Dolorosa shared this ability, as Mindfang and Aranea's narratives do not convey any details about her after her assassination. It should, however, be noted, that her eyes are shown to have the bright yellow glow sported by rainbow drinkers. Later conversations between Kanaya and Porrim confirm that being a rainbow drinker indeed directly relates to having jade blood. Kanaya also stated that their caste must have developed these abilities after working in the dark birthing caverns, while Rose suggested that the ability could have been developed to scare predators away from young wigglers.

Teal Blood
Teal / Aqua Blood is considered a high class in Alternian society. As a chromatic median between the green and blue castes, teal blooded trolls are not quite considered nobility, but still outrank the middle-class green blooded castes. Trolls of this blood color typically take civil servant positions, such as that of a legislacerator. According to Mindfang, typical lusii for this caste are cholerbears and spleenfowls, both are implied to be big enough to carry their trolls.

Terezi Pyrope and her ancestor Neophyte Redglare fulfilled their roles as teal blooded trolls. Neophyte Redglare was a legislacerator, the Alternian equivalent of a lawyer who also doubles as a bounty hunter, and Terezi hoped to one day also have such a role in the Alternian legal system. Both also had dragons as their lusus, which Mindfang stated was quite unusual for a troll of their blood color to have, and used their verbal prowess to affect others, rather than any sort of psychic ability. As Latula comes from Beforus rather than Alternia, it is not known what was expected of her as a teal blood.

The "Rebel Marshall" from Hiveswap is a tealblood.

Cerulean Blood
Cerulean / Cobalt Blood is the first rung of nobility. It is suggested that cerulean blooded trolls are unlikely to develop psychic powers. Usually this blood color is simply referred to as "blue," which can cause confusion as indigo blood is also referred to, and appears to be, blue. A potion presumably based on her blood is referred to as "cobalt." However, Vriska herself called her blood "cerulean."

Vriska Serket, her ancestor Marquise Spinneret Mindfang, and her dancestor Aranea Serket all have cerulean blood. All three of them are very powerful psychics who are able to manipulate the minds of others to bend to their whim. All of them also have vision eightfold, allowing them to peer within the Magic Cue Ball to discover its secrets. Aranea confirmed that psychic abilities related to mind reading and manipulation are an occasional phenomenon amongst cobalt blooded trolls. It is not known if this goes hand in hand with vision eightfold, or if this trait is simply unique to the paradox clones.

Mierfa Durgas is stated to be a member of this caste by her creator but appears to be listed as Indigo in Hiveswap judging by the prefix on her 2D image. The "Pirate Thief" from Hiveswap is also implied to be from this caste as he is prefixed with BL, distinctly separate from I.

According to Porrim, this caste is male dominated, or at least it was on Beforus.

Indigo Blood
Indigo Blood is the second-highest tier of blood amongst the land-dwelling trolls. They are considered part of the nobility, and as such they have a traditional rivalry/mutual kismesissitude with the sea-dwelling trolls. They are prone to violence as well because of their location on the hemospectrum. As with cerulean blood, this blood type is commonly called "blue," but the color has been alternately referred to as "indigo" when used as ink or in a potion.

Equius Zahhak and his ancestor E%ecutor Darkleer are both indigo blooded trolls. It is stated that Equius's enormous strength is unique to himself, rather than being characteristic of the indigo bloods. It is unclear if the same goes for his ability to regenerate his teeth. While Equius's strength would enable him to be an effective ruffiannihilator, he would prefer to be an archeradicator (an elite archer of the imperial forces and a role shared by E%ecutor Darkleer), in keeping with his Sagittarius theme. Both Equius and his ancestor are also skilled in robotics.

Aradia became an indigo blood when her ghost inhabited the soulbot Equius constructed for her, and she became much more violent (a trait absent from the lowblooded castes). Horuss Zahhak also has indigo blood and shares his great strength with Equius, although this is stated to be because he is a bodybuilder, amongst other endeavours.

The HS 4111 (archeradicators) are known to include indigo bloods.

According to Porrim, this caste is male dominated, or at least it was on Beforus.

Purple Blood
Purple Blood is the highest ranked blood possible for land-dwelling trolls, and members of this caste are referred to as the "highbloods." Because of their position on the hemospectrum, purple blooded trolls are more prone to extreme violence and unpredictability, and it was for this reason that most were tasked as the violent subjugglators under Her Imperious Condescension. Andrew Hussie stated that all the purple blooded trolls are adherents to an Alternian Juggalo-like cult that believes that "a band of rowdy and capricious minstrels will rise one day on a mythical paradise planet." Hussie also suggests that purple blooded trolls are granted psychic powers (the "chucklevoodoos"), which permits them to keep the lower blood castes in check. Gamzee's psychic powers (possibly augmented by his Bard of Rage powers) allowed him to HS 5928 (facilitate the appearance) of a harlequin Jack Noir doll and Dream Cal in John and Dave's respective dream towers (dream rooms reflect the subconscious of players, so it's not clear if Gamzee was using a form of telepathy or conjuring the objects directly). Kurloz has demonstrated the ability to engage in two-way telepathic communication (possibly limited to eye contact), and what appears to be some sort of hypnotic gaze power.

Gamzee Makara, his ancestor The Grand Highblood, and his dancestor Kurloz Makara are the only purple blooded trolls that are of note in Homestuck. The Grand Highblood served as a subjugglator, and it was Gamzee's ultimate goal in life to eventually take up this position himself. All of the purple blooded trolls are also highly violent and unpredictable, but it is only after Gamzee runs out of the narcotic sopor slime that his true purple blooded nature arises. It is notable that Gamzee used an immense amount of psychic power, after becoming sober, to make the kids' session "terminal" (by creating a harlequin doll missing an arm and an eye in John's dream self's room, causing a chain reaction of events). Kurloz also displays great psychic power, using it to command Meulin into serving himself, Gamzee, and presumably Caliborn. As it is a median color between the blues and the sea-dwelling purples, it is fitting that Gamzee lives on a shoreline and has an aquatic lusus. The only other lusus that is shown is a whale with purple blood, suggesting that all purple blooded trolls have aquatic lusii, but live on land. That would also mean it's common for purple bloods to live on the coast shore, to be close to their lusii as they would be out of reach otherwise.

According to Porrim, this caste is male dominated, or at least it was on Beforus.

Violet Blood
Violet Blood is the second-highest color of blood in the hemospectrum and is the first of two that exclusively belongs to sea-dwelling trolls, which are noted for their ability to breathe underwater, fin-like protrusions from their neck, and collapsing and expanding bladder based aquatic vascular system (which is merely a fancy term for the heart). Violet blooded trolls tend to be more violent than the others seeing as they are high on the hemospectrum, and express an extreme hatred towards the land-dwelling nobility. They also tend to be affiliated with piracy and are considered a part of the aristocracy. Karkat calls this blood type "purple" once; this was before coloUrs and mayhem: Universe A came out, and the blood colors were not consistently named.

Eridan Ampora, his ancestor Dualscar, and his dancestor Cronus Ampora are the violet blooded trolls introduced in Homestuck. Both Alternian violet bloods are violent towards the land dwellers, and both sought a kismesissitude with their generation's main cerulean blooded counterparts and a matespritship with their fuchsia blooded counterparts. Cronus, the only known Beforan violet blood, does not display the same violence towards land dwellers as the others, as it was not the norm in the peaceful culture of Beforus.

Nektan Whelan is also a member of this caste.

Fuchsia Blood
Fuchsia Blood is the highest and rarest color of blood in the hemospectrum. Like their violet blooded comrades, they are sea dwellers and are considered royalty. Fuchsia blood is so rare that those who possess it are destined to be the sovereign of all trollkind.

Only two trolls at any time have this blood color, an older one serving as the Empress of the trolls and a younger one known as the heiress to the Alternian throne; this is due to the Condesce killing her descendants once they've come of age. Both are linked to the same lusus, Gl'bgolyb, known as "The Rift's Carbuncle", "Emissary to the Horrorterrors" and "Speaker of the Vast Glub", who HS 5963 (compels) the younger troll to challenge the older for control of the throne.

Gl'bgolyb must be kept quiet by the fuchsia blooded troll, as Gl'bgolyb's voice is capable of killing trolls in ascending strengths and numbers depending on how loud it is, with the lower castes susceptible to anything above a whisper, to the devastating Vast Glub which kills all trolls in the universe save for the two fuchsia bloods.

Feferi Peixes and her ancestor the Condesce are the only two fuchsia blooded trolls alive during the events of Homestuck, with the Condesce serving as Empress of Alternia off-planet leading the conquering forces, and Feferi staying on Alternia to tend to Gl'bgolyb. Because the Condesce is far away from Alternia, her psychic connection to Gl'bgolyb is severely weakened; as such, Gl'bgolyb's allegiance sways to Feferi.

As a member of the top blood caste, the Condesce is given a much longer lifespan. She also HS 5960 (has the ability to extend the lifespans of others), but it is unclear if this is related to her blood color or her pre-scratch self having been a Hero of Life.

Due to the events of Sgrub, neither the Condesce nor Feferi are capable of preventing Gl'bgolyb from releasing the Vast Glub, killing all trolls in the universe save for the Condesce, Feferi, the Handmaid (whose meteor lands in the future rather than the past), and the Sgrub players who manage to escape into the Incipisphere. Notably, Sollux and the Ψiioniic/Helmsman die due to the Vast Glub, but Sollux's multiple dream selves let him survive to play Sgrub.

Meenah Peixes, being the pre-scratch version of the Condesce, also has fuchsia blood, but she rejected the throne as it meant serving the entirety of Beforus rather than ruling over them with an iron fist.

It should also be noted that another lusus with HS 4361 (what appears to be fuchsia blood) is fed to Gl'bgolyb. Whether or not this is evidence of other possible trolls with fuchsia blood is unclear.

In Hiveswap there is another heiress with fuchsia blood, also appearing to be from the Peixes line.

Trivia

 * Most of the blood colors are distributed at 30° angles on the HSV color system, varying by a few degrees here and there. The only exception is that lime blood is 73° instead of 90°, and olive blood is at 82° instead of 120°. This was probably done in order to make the different colors more visually distinct. Most of the colors are fully saturated (and the rest are close), but their brightness values have a wide distribution.
 * The prefix hemo- means blood, and a spectrum is an array of colors; thus, a hemospectrum would be an array of blood colors, as it is in Homestuck.
 * The only notable Alternian native other than the trolls and their lusii is His Honorable Tyranny, whose blood is HS 5654 (pure black).
 * Nepeta's walls are covered in red blood, indicating that most of the Alternian fauna have red blood, and that the hemospectrum is unique to the trolls and their lusii.
 * It's possible that the variation of blood color itself is based on the blood pigments used by arthropods in nature (upon which trolls appear to be based). The predominantly land-dwelling insects use hemoglobin, which is a familiar red, while horseshoe crabs and many of the mostly sea-dwelling crustaceans use hemocyanin, which is dark blue when oxygenated.
 * The association between highbloods, royalty, and the sea probably comes from the nature of the last three signs of the zodiac (upon which the trolls are based) - Pisces (the fish) and Aquarius (the water bearer) are entirely aquatic concepts (just as Feferi and Eridan are entirely sea-dwelling), and Capricorn (the sea-goat) is a mixture of land and sea creatures (just as Gamzee lives by the sea, but not in it).
 * In the second walkaround of Act 6 Intermission 3, both wrigglers have a skin color that is similar to burgundy and bronze blood. This could imply that wigglers have a skin shade that is slightly darker/lighter than their blood color, as Andrew Hussie had previously stated that there are only twelve possible troll blood colors, excluding mutations.
 * Various groups have been mentioned with uncertain positions on the hemospectrum:
 * It's not clear if the HS 4656 (blind prophets) were an organization, or if it's just a collective term for a series of historical figures with prescient psychic abilities.
 * The HS 5962 (laughsassins and ruffiannihilators) have also been mentioned as branches of the Alternian military. Their caste restrictions are unknown, however the laughsassins HS 5886 (appear to be affiliated with the subjugglators in some way), perhaps as either a branch of the subjugglators or an organization under their command, and Equius was HS 4111 (said to be qualified) for joining the ranks of the ruffiannihilators.
 * The HS 5927 (scienstiffs) are mentioned as a historical group which drew the ire of the subjugglators.
 * The fact that jade bloods (and thus Rainbow Drinkers) can withstand the sunlight is a reference to the fact that human vampires (which rainbow drinkers are the troll equivalent to) cannot stand the sunlight. On Earth, normal people are awake at day and asleep at night while vampires are awake at night and cannot touch sunlight - on Alternia with regular trolls and rainbow drinkers, this is reversed.