How do they make coloured shapes and lines on ice rinks?

Answer 1

After putting on a few layers of ice and grooming them smooth, the lines are laid out with paper, like toliet paper, then the next layer of ice is put on, then succeeding layers above.

In the same way some rinks have logos put in them.

Answer 2

Any pattern you see is under the ice. In a rink, the ice is usually less than an inch thick, so any pattern or lines you see are actually painted on a sub-floor beneath the ice, but above the cooling elements that keep the ice frozen.

Answer 3

I've always assumed that the lines are on the floor beneath the ice, not on the ice itself (ice is usually clear).