Many things can cause hair color change. Thyroid imbalances, skin wounds, including vaccines, sun damage, the dog itself if he is biting or scratching the area. Most changes are temporary, but it could take a few months for the hair color to restore itself. Happens to well bred dogs too! Might want to have your vet give him/her a good going over and maybe do some bloodwork just to rule out anything going on medically.
