Indigo caste

The title of this article is a combination of two terms which have not been used together canonically, but is based on their use in the comic. "Indigo Signs are the enthusiasts of the sign classes. Friendly and cheerful, their optimism is contagious. Being around a well-adjusted Indigo Sign is always a good time. It's hard not to be drawn into their excitable orbit, just like they are drawn in by anything and everything that piques their interest. And those interests are liable to change at any time. Indigo Signs will often surprise their friends and family by declaring they are no longer interested in what just last week they were claiming was their jam. If you catch an Indigo Signs in a philosophical mood, they can be unexpectedly poignant and introspective. A downside of all this jovial enthusiasm is that Indigo Signs often don't know their own strength. They are known to be careless, both physically and emotionally, their conversations punctuated by jostling elbows and tactless comments. They don't usually mean to offend, and are often shocked to find out they upset anyone. When this happens, they can dig their heels in and insist they did nothing wrong. In romance, Indigo Signs need partners who can keep up with their expansive personalities, as well as forgive them for the occasional hurt feeling or two."

- The Extended Zodiac

The indigo blood caste is one of the twelve troll blood castes, higher than blue and succeeded by purple.

Names
In Homestuck, this caste was generally referred to as HS 2211 along with cobalt and teal. The name 'indigo' was introduced by coloUrs and mayhem: Universe A and reappeared on the Extended Zodiac.