I have an interesting question for you. My dark bay has developed spots. When we clipped him last year, and for the duration of the time I've had him he's never had them. This year (he is 7), about a week after he was clipped he started growing in funny spots in no real pattern, mostly on his barrel. He is usually nearly black in the winter and in the summer his coat naturally is very bay. We clipped him about the same time both this year and last. He also has natural white hairs mostly in his tail and 5-6 in his mane.
His sire is black and his dam is a bay.
What could be causing his spots??