The other week I made sidewalk paint for Xander. It was extremely cheap and easy to do.
What you need:
Corn Starch (4 tbs per paint color)
Water (2 tbs per paint color)
Food coloring (I used 5 drops to get the color I wanted)
Containers to store the finish paint
Place 4 tbs of corn starch in each container:
Add food coloring:
Add 2 tbs water:
Store in containers:
Our paint lasted about a week. We just had to stir the mixture prior to using it.