Here's what you need:
- food coloring
- small containers (I used cupcake tins from the dollar store)
- paint brushes (the cheap foam ones work well)
Here's what to do:
1. In your small containers, add equal parts cornstarch and water. I used a little less than 1/4 cup of each for our paint. Mix the cornstarch and water well (it'll be gloppy at the bottom). Add several drops of food coloring to each container to make the colors your children want and mix well.
2. Paint away! The paint will go on rather watery and dull, but will dry to a nice bright pastel. If your driveway (or other painting surface) is particularly smooth or bumpy, you might want to experiment with adding a little more or less cornstarch to get the coverage you want, but the equal parts ratio is a good starting point.
3. My kids like using the paints for free form painting and also like drawing an outline with sidewalk chalk and coloring it in with the paint.