To prepare for this activity, freeze a tray of ice cubes with a drop of food coloring in each section. I used yellow, blue, and red food coloring. Put them into a sand or water table filled with water. If you don't have a water table, you can use a large container or bowl of water.
Once they are dumped into the water, the colors start to stir, swirl, and mix. TIP: It's better to do this activity in a white or clear container, table, or bowl. The red bottom of ours took away from the actual color mixing.