Mix first 4 ingredients in a small saucepan with a whisk and heat over medium just until it starts to thicken. Remember that cornstarch-thickened sauces get more gelatinous as they cool, so you don’t want to cook it too long!
Spoon into jars, add food coloring, mix and allow to cool. Yields approx 1 Cup of paint. Can be scaled larger if you need more. Be warned that food coloring DOES stain, so be sure to have the kids don aprons or old clothes to prevent nice clothes from getting ruined. For fun, you could add a few drops of flavoring extracts to make them smell yummy, and even make different colors different scents!