Would you really wanna smoke food coloring? Iv herd of organic coloring that works, but can't give you much more info seeing as I never bothered to store the info. But Im sure you can simply do a search and find one of the tons of threads that ask this question.
I have heard of people using it for certian flowers, to change there color. A friend of mine used it once. It did effect the flavor just a bit. I wouldnt suggest it, but if you do. just do it to one and taste the difference.