I think this craft is pretty self-explanatory, but just in case, here goes:
Coffee filters (we didn't have any, so we just cut round circles out of a crumpled piece of packing paper I found in one of my unpacked boxes. Yes, still a lot of unpacked boxes here.)
Paint the circles with watercolors, allow to dry, then clip in the middle with a clothes pin. I used scotch tape to tape them to our playroom door, but I think these would make a cute mobile too. Hm....