Yes, it can be bred out if need be. Just like Champ was saying. If however you have extra males without bit, I'd recommend just using them instead . It is a DQ for showing. If you aren't showing and hes a good type, just use him over solid girls.
There is an thing that causes pigment to turn white. Can't remember what its from. Someone once said its from damage cause by various illnesses yet the bird recovered . Who knows.
But as the birds age, with each molt they get whiter. First year with it they just all of a sudden have a few white tips.
The second year, they look mottled.
The third year they are almost if not , solid white.
I have seen it in 3 birds here over the years in different breeds. But was all in hens.
This is not hereditary and they continue to breeds true and clean.
If he gets whiter with age , that could be the problem.
However if his chicks end up with white after they mature, then its genetic flaws