One of the best ways to teach children about colors is to give them opportunities to mix them up and see the result. You can talk about things over and over, but until you give some the chance to have a hands-on experience, you're wasting your time.
Here are some ways to mix up some colors with less of a mess:
1. Rolling Box: Use a shoe box, marbles, paper, and paint. Put the paper in the box, add some paint and marbles in the box, put the lid on, and shake it up. Test out different colors and combinations.
2. Paint Bags: Use a zipper sealed bag. Add two different colors and see what happens when the bag gets squished.
3. Playdough: When you make your own, mixing the colors won't cause a problem. Make a batch and separate it into three sections. Add red, yellow, and blue color to those sections. Then let the kids mix it up.
Here are some ways that can make a HUGE mess ;):
1. Finger Paints: Better put down a plastic tarp and smocks. You'll still get paint everywhere but you tried ;)
2. Food Coloring: Put some drops of food coloring in water and let the kids mix up spoonfuls. Just don't wear anything you want kept stain-free