M and I had fun the other day mixing tempera paints. "Let's see what color we get when we mix a little (yellow) into this (red) paint." I would say. "Orange!" she exclaimed as the colors began to mix.
After the paint was mixed into a new shade we used a cotton ball to paint one pocket of an egg carton. We painted a small rock the same color. Once every pocket and rock was painted we left it to dry for a couple of hours. When we came back, M had a new game for matching (find the rock that is the right color to go in each pocket). The nice thing about this toy is that the lid can be closed and so it can be carried around easily.
The bad thing about this toy (as we discovered) is that if you leave it outdoors to get rained on, you are back where you started with a gray rocks and a dingy egg carton! :-)