I know that this is a very popular lesson, and after doing it myself, I see why. I read the story "Mouse Paint" by Ellen Stoll Walsh to the Kindergarteners, and they learned what two colors mix to make which secondary colors. We went over the color wheel, and made one ourselves using mice. Students used oil pastels to mix the colors, and then cut them out and place them in a circle. They loved adding the final touches.
Concepts: The Color Wheel, Color Mixing
Materials: White Construction Paper, Tag Board, Oil Pastels, Scissors, Glue