My opinion on this is that there should be set amount of colors, say RGB + Black, and White.
Potjeh's example of using a two item recipe is ok, but for something more complex like bread, it'd be a lot to code.
You'd have to keep your crops all one color, or even so, find the color you want, randomly in the woods.
Then you might need to find the right water, and would brick/oven color + fuel come into play as well?
Then try and do it for something animals, how would you know what color an animal would be?
It would become a lot to do, as much as I love the sound of it.