User blog comment:ZoshiX/Notes on Aura/@comment-16075172-20140903155747

Also: Ones aura is usually based on their blood color (This is mostly for Trolls, but sometimes is true for Serrangios), eye color (Humans like the kids from Homestuck as an example for this, though some dark matters may also count), or other things (Symbol, Pestertag color, etc.). The color of one's aura may be changed through some things, which includes some time shenanigans (Beta/Gamma LAT as an example) or auric purification (HS 7F7F7F (Purified Mori) for an example.), or something else. Auras can be passed down through genetic similarity (02 and Kuipter have the same aura as Revelian, Hank Anagram and LD have the same aura and others in LD's family have green auras, etc.). One's auric scent can be changed through a magic ritual (For an example, I'll say that Hankvi changed his auric scent from grapes to sulfur when he became a follower of Chaos.).

I think this is it, unless there's anything else you need to know.