the proteines that make up your hair and fingernails can store some color coming from foodsources.( for instance,carotene can give a nice golden shine on all types of brown hairs )but it's all genetics folks, it can be passed on through breeding, it can be a hidden factor on one deer and color another deer, just like every other natural feature on an animal.
It takes something like evolution to really make environment or habitat a key factor in color changing and if that's the fact we need a few hundred generations to study before seeing results........

F.