Bah, so I cannot find the page that includes information on it. But if I remember correctly it's because when they're used for hunting, the white color makes it so others can see them. Which is why they don't prefer to work with white ones. There are also some talk that white ones have serious health faults, which can effect their hunting ability too.
Ah yeah, that too. I know breeders, ecspecially those that work/show try to not breed two white shibas together, ah I had so much information on this the other day but now I can't find any of it >.< Wish I had bookmarked it.
Anyway, I think I'll breed the reds first. Once their puppies are sold I'll breed the Black/Brown pair. Probably have the first pups up tonight(so much for waiting till get a waiting list XDD)