I've painted my tubes black with nail polish - so-so idea.
The polish never really dries out on plastic (or latex, whatever it is),
so if you rub the tube too hard it sticks to your fingers and comes off the tube - messy.
but it does cover well otherwise. it won't peel at least, and no it won't color your skin.
btw I have no idea what kind of the tubing I have, but my guess is the cheap ones..
Fuzzy