I think diet, sun exposure, and water can all effect color of plumage. A high mineral content in hard well water (iron for example) can also show itself.
I agree with Tim on the corn, the ingredients in corn would likely still be the same in which ever form, be it whole, ground, crumbles, or pellets.
I never did see the draw for cracked corn, the quality starts to degrade as soon as you break that kernel. . My daughters old english games could swallow whole kernels no problem, I've cleaned both dove, and quail that had corn in their crops. I do make one concession, when the young birds are first on the ground I often put an old male in with them, for two reasons. One is to kind of ride herd over the young bucks, keeping the earlier hatched chicks from being as rough on the younger ones. And secondly he will clean up the corn from the limited scratch I throw untill they are big/brave enough to start eating it.