Dunmeri eyes are bloodshot, like in previous games.
Altmeri eyes are normal, like they were in previous games.
Woodelves have tiger-like eyes (So in theory, pupils expand and eyes look black. On textures pupils are contracted so you can see the color and the texture of the iris!)
"Demon" black eyes are now daedra eyes, like they were in Oblivion (used by Golden Saint and Sheogorath). Play as daedric prince in disguise instead of "what, sorry, black eyes, why?"