Place a rack on a bucket (or something similar) to collect the paint you spill. Then put the stones on this rack. Pour two different colors of paint in a cup. Don't stir! Then pour the paint over the stones, make sure to cover every part of them. My girls are 3 and 5 and could do this themselves. It made them really proud :-) The stones will take some time to dry, at least 24 hours.
I let my Geeklings pick the colors they wanted to use and was suprised by the combinations they chose. They worked really well, even if I didn't think they would. The result is a hand made treasure.
Tamara, Geek, mother of two Geeklings, editor.