Right so this may be a little off topic, but I was hoping someone here might be able to help.
So as some of you may know, every year home depot has this backyard rink contest. I have made a backyard rink and would like to enter it. However one thing that I would like to do to make it look better is to put lines on it. My problem here is that for the base of the rink I used a frozen pond. Now if I was to just paint the lines, eventually the ice would melt and the paint would go into the water, which I don't suspect is good for anything living in there. So is there any way to paint lines on the ice that would: 1) not be harmful to the environment, and 2) not be illegal?
Painting ice is a bad idea. Apart from the environmental problem you already listed, I doubt you could get regular household paint to stick to ice. And even if it does I doubt it would dry properly. You might try food coloring (which is environmentally safe) but it's going to get all over your clothes any time you slide on the ice.
The only solution I have is to use a liner that already has the lines on it. Put the liner on the ice, fill with water, and freeze. Seems like a waste of effort, though, if you already have a frozen pond.