I Know someone that as tried something similar to this but they said to flush the plant 1 to 2 weeks before harvest with like at least 6 gallons of water, let the soil dry all the way up, and then add the half gallon of grape juice (i guess mixed with like some water. and then let the soil dry and cut down the plants. He did it and it had a noticable differents on the tast of the one plant he tried it with. some GRAPE FRUIT FUNK. it will make your bud extra fruity,i don't think if effects the color though. i'm going to be trying it in a week.
a food dye diffently might change the color of the plant though at the end of harvest, or after clipped and put in a vase over night. it's all worht trying if it adds extra flavor to the bud, vanilla,hawaiian punch, coco kush, any sugary drink that has water added to it will work, pineapple,.
the color dye howeer might change the color of a plant if added to last watering of a plant before cut, but i dunno, u might also have to had it to a vase of the color dye over night to effect the color of the plant, but the PLAnt will suck up any water it is given if it is a healthy plant