Here's the recipe for homemade paint: (tweaked a bit)
Stir ¼ c flour and 1 c water together in a saucepan. Mix well. Heat until mix thickens. Remove from heat. Add 12 T baby powder and food coloring. Add 2 t laundry detergent (for glossy finish) or 2 t liquid fabric starch (matte finish). Mix well. Pour into small containers and add food coloring. (I'm sure 12 T could be made easier, but my measurement conversion chart and all cookbooks are packed....)
It worked pretty well. We found that using it thick and heavy worked best for coverage. It dried nicely (although not glossy even though we used laundry detergent). It smelled really wonderful, like a baby! Bee painted lots of fireworks, which is her new obsession... poor thing has never even seen real fireworks.