Your child is already painting, as if he knew how to mix them, getting new colors? If not, explain how this is done. For example, prepare three glass jars. In one dissolve a little bit of blue paint, the other yellow, and leave the third empty. Ask your child what color do you get if you mix these paints. Let him mix it up in the third Bank. Now you can experiment on the palette or on a sheet of paper. What color do you get if you mix red and yellow? And red and blue? From mixing any colors will work just dirt?