Our first experiment was making some marbled milk. We found this over at Surviving A Teachers Salary
This one I found on pinterest, from Create Studio. We put water in plastic ziploc bags, then added the primary colors (1 per bag). Then we got to experiment putting the bags over each other to make the different colors.
This is one of the pages we did from her preschool book. After coloing the food, we sorted it by color into "shopping carts".