dont think it would hurt them at all, but i think you would just have blue stained roots and thats it. also wouldnt do it cause there is no real reason to do that except to try and sell some bagseed as a well known and liked strain, in other words to rip people off. bad business bro., if you just want to have blue weed for yourself to smile about and show your buddies, give it a try, only on one plant as an experiment. if it dont work, spray a bud like mentioned above (small bud in case it messes it up)