Homemade Sidewalk Chalk Paint

We are having a mellow summer this year, but D has big plans for all the crafty things she wants to do.  First up is chalk paints.  Her teacher filled me in on an easy, homemade version- cornstarch, water and food coloring.  I'm guessing there are actual "recipes" all over Pinterest.  These took about five minutes to mix up- she's been painting the driveway for days!