Yes. Yes. Yes. * And Yes.
*However, we have owned horses with a blue eye and got along
fine. Sometimes it helps to paint a black circle around the hair
by the white eye to help with light sensitivity.
Unless I really liked the horse for some reason, I'd not buy
a horse with a blue eye. But I wouldn't say I NEVER would
buy a horse with a blue eye, either.
If you are talking pink skin, a white horse and blue eyes
(called an Albino) they can be blind, deaf or not affected.
One blue-eyed paint horse than has won major shows
is deaf. Here's a link to that individual. "Gunner" aka Colonels
Smoking Gun. A high percentage of
his offspring are also deaf.
I own a black n white paint now with a blue eye and we've come to the conclusion that it does affect his sight in some situations like crossing water with reflection, he really puts his head down and studies the water before he'll take a step. Just riding and moving cows in general though it doesn't seem to bother him. Shadows in canyons though make him watch his steps more too.