Dye sets into the plastic. Once it is pulled out of the dye bath and rinsed off it's in there for good. I have had no problem with it leaching out or problems with oil reacting to the dye. I just rinsed the parts well to make sure all the salt was removed from the plastic parts and re-assembled them. They look cool and makes it easy to color them different for different loads and you can still see how many rounds remaining in the loose mag verses the black ones where you can not see anything but the next round.
Kevin - I would not thing you could do anything to the black ones since the plastic is already black and the dye would not make a difference.
I have seen others color the clear mags blue, yellow, green, smoke and orange. Looks like them old candy suckers on a stick you had when you were a kid !
APEXDUCK