Chromatography: All you need is markers, water and coffee filter. You can even do this by cutting one coffee filter into strips and putting a dot/line at the bottom where you will add the water. Let the coffee filter draw the water through the maker and it pulls apart colors.
What is Chromatography? The separation of a mixture by passing it through a solution.
In this case it is marker pigment and water. Did you know there are hidden colors in your markers? try different ones and see what happens.