Anon's favorite color is green, and green is the opposite of red on the color wheel, his least favorite color. He wants to distance himself from the color red as much as possible, explaining his tastes and appearance.
In Oure's route, Essi finds a comatose Oure underneath the institute, where he was kept alive by the massively creepy Loil, who even admits that he was going to get rid of him once he got older. However, he kept him because of his youthful face. All kinds of Squick and Fridge Horror arise from the possible implications, from Beautiful Dreamer to Dude, She's Like in a Coma.
For the most part, Yuon is turns out okay if you don't pursue his route. Oure and Anon, on the other hand...
Oure: Because Oure is aging, he is losing the ability to create his Astral Projection. When he loses this ability, he will be useless to the institute's research, and thus they will not have any need to keep him alive.
Anon: Anon himself is a serious Death Seeker, and he isn't able to dig up much on his past without Essi's help, so he'll eventually be Driven to Suicide.
