I know this is completely off subject but I just read Jash's Craglist thing in his sig... lol that is some funny shit- reminds me of when I was a little younger.
Just to comment on the OP... I don't think it would work... I may be wrong because I am also too lazy to google this but.. Again I'm not sure how food coloring works exactly but just like you and I, we have metabolisms. Plants too have something similar I think, just much simpler in a way. If I was to drink/eat food coloring, I wouldn't expect my natural pigment to change... nor would I on a plant because they use what they need and don't uptake or expel what they don't.
Possibly change the veins in the leaf or maybe the hairs but I really doubt...
For some reason, if this did work- I think there would be a lot more people claiming a lot better shit than they really got. BTW and not to criticize your experiment, I really wouldn't want to smoke food coloring.. even if it did work.