mushroom coloring

[philosophile]

So I was wondering if anyone knew how mushroom colors develop... I have a shroom that I fragged, whose foot grew into a green kinda white striped mushroom, but the head never had any white to it.

I know some mushrooms develop different colors if less light is given, others develop different colors if more are given....

So how does this all exactly work? Is there any way to encourage a particular color (knowing that the mushroom is capable of that color)?