We set out 7 cups and then we put water in every second cup. We put red, yellow, or blue food coloring into the water filled cups. Then we folded up 6 paper towels and put them into the cups. One end went in one cup and the other end went in the cup next door. We waited for three hours and this is what happened. The water moved into the empty cups through the paper towels and made different colors. We started with red, yellow and blue. We made orange, purple and green.
When we got back after leaving the water and paper towels in the cups over the weekend - look what had happened! All the cups had an equal amount of water. Plus our yellow water had turned orange, our green water was very green and our purple water was really purple.