You can do this and pretend that you are at the makeup counter in a major departmet store. Try this again and match the skin colors of your friends. You are all made up of some combination of red, blue, yellow and white. Try putting thumbprints of all the different skin colors on your paper. Then add arms and legs as well as facial features for a truly wonderful, multicultural image.
Resources Here are some other artists who used color in different ways.
Look for the primary and secondary colors in their work.