I set up some clear glasses with red, yellow and blue food coloring in a circular fashion. In between each primary color on the wheel was a cup of clear water. So the formation was similar to a color wheel. We then added food coloring to the clear cups, using the two colors that each cup sat between.
As we mixed the colors, Miss O used colored pencils to fill in the secondary colors on her color wheel that is already attached to her color lapbook.
They seemed to need more to really believe that the primary colors made certain other colors when mixed, so I whipped up this little worksheet right then. They liked this so much they did it twice!
I squirted a bit of red, yellow and blue paint in the rectangles to the right. Then I labeled the circles with the first letter of the color they were to paint in that circle. For the last circle, they dabbed their brush in both colors and then mixed it on the paper.
Both these and the primary color quilts are hanging on the door of our pantry. It's a good reminder for them and they tend to reference the projects when I ask them what the primary and secondary colors are or when I ask them what two colors make when mixed.