summerback?

I knew a tb that had black skin, dark bay hair. In the summer, his muzzle and around his eyes would get black. What happened was his hair would thin out in the summer and therefore look black on his muzzle and eyes. Not to sure about anywhere else but it was very noticeable on his face.

Yeah I know of a couple of TB like that.... But what mathew is referring to is sun bleach..............