Here is one for yall... We have a half arab / half walker cross. He is nine years old.
Never has he had any white hairs anywhere, and now all of a sudden he is developing white spots everywhere! On his neck, face, and mostly butt! He does have some on his back, but the largest are on his butt and neck. We are now jokingly call him our "air-walk-aloosa". He is not sore in any of these areas.
He is pastured with a few paints.... Maybe he likes the way they look? I am hoping this isn't anything to worry about.