Something that's always confused me is why did Terezi's eyes turn red when she was blinded if her blood is teal?

There’s a theory saying that in troll society bright red=damaged.  Terezi’s eyes were damaged and turned Red.  Karkat has something wrong with his pigment gland and his blood turns red.  Wearing bright Red gives the illusion that the troll was gravely injured and is walking around like it’s nothing, possibly why Vriska and Terezi wear red shoes, to intimidate their opponents.