Not so easy to take a picture of these kids!
To start with, the left cup had red water and the right cup was empty. One end of a piece of rolled paper towel was placed in each cup. It took a LONG time, but the water transferred to the empty cup.
Here we put yellow water in one cup, blue in the other. They mixed into a little bit of green in the middle, but that was all. Since there was the same amount of water in each cup, it wouldn't continue to the other side.
This part was really interesting! We made brown water by adding red, green, blue, yellow, pink, and purple food coloring. Green came through to the empty cup first, and then a pinkish color. It eventually turned the water in the previously empty cup a more brownish color, but it stayed greener than the brown water. Once each cup had the same amount of water, no more water transferred between cups.
Hunter said all they did that day was watch! I may have thought it was more fun than them. :)