Greys don't sunburn, but they can get melanomas. I haven't experienced this first hand, but I have read that something like 80% of grays will get melanomas. The good news is, they often time don't spread and the horse can life out their normal lifespan with them. I HAVE heard of them spreading/growing though.
Anyway, my girl is fairly large, around 15.1, 1100 lbs. But she sort of has to be, because I weigh around 200 lbs myself and didn't want a horse I would feel to big to ride.
I think my mare used to be black. All her fleabites and a spot on her forehead are black. Black is my favorite horse color and so I will sometimes tell people I finally got my black horse with Isabelle and they look at me all weird.
My "black" horse: