Use a simple grid design like in my Art 1 spectrum color wheel designs.
Instead of using the chromatic scale have them start with a pure color like
orange. Then have them add a small amount of blue to the orange to dull it and
paint it going a way from the first shape. Repeat this adding blue to dull the
orange more and more. Pretty soon if there are enough shapes it will become
blue. It takes about 8 or nine shapes top do this. Look on my site for the art
1 spectrum designs and then look for the yellow area replace the letter with a
warm color and go from there. I have a ton of slides of this I could mail
them to you.
Art teacher, Leigh High School, San Jose, CA