Re: White boxers - what's wrong?
I don't believe so... Interesting theoretical question though!
Where a boxer is white, that's an area of little or no pigment. Whites aren't entirely unpigmented of course - we see pigment spots on the skin (that which isn't "strong" enough to also colour the hair, but appears as skin spots or "freckles") and we see pigment in the eyes and nose leather. And any areas that are coloured, of course. If you were to breed white to white, without exception, every single puppy would likewise be white (or mostly white) and pigment would be diminished with each successive generation. So - fewer coloured patches, fewer skin spots, and very likely also a vastly increasing incidence of blue eyes (which is also due to lack of pigment) and increasing incidence of deafness. But I don't think that this leads to zero pigment. If we could calculate it mathematically, I think we'd (eventually) see pigment approaching zero - but never quite getting there.
Albinoism is something else entirely. It is caused by gene defects that lead to an inability to produce melanin. Quite possibly the effects of near-zero pigment, even if by different cause, could have similar health effects though (eyesight loss, lung and bowel diseases, etc). Fortunately, white boxers aren't in that sort of extreme category.