It’s colorful, cheap, and a little bit slimy. What’s not to love? Goopy goop, is pretty much colorful paste. Get a few of the plastic bottles they sell for hair dye. Fill them about 1/2 full of flour. Add water and food coloring or water color powder. Adjust the flour to water ratio if necessary so that the goop is thin enough to be easily squeezed out, but thick enough that you can basically write with the stream that comes out. I used it in my sensory bin and included some paint brushes for mixing colors.