If you look closely you see the DAM's eye is weird. Yes it is very possible for a Horse to have a single multi-colored eyes, I happened to see it myself in real-life. And Boy was he Purdy. His other eye was blue though and he inherited it from his dad. Yet it was a very run down ranch taken care of by a single women and she is a bit too old to be doing it by herself. But we moved to a much better place now and thinking of moving our horses again.
(C) me not the lines nor the species.