While I was in for an art teacher at another school, she had a lesson planned for teaching warm and cool colors. The students had already done the warm color component which used shapes to create an abstract design that was painted with warm color tempera paints.
When I was there, they were on the cool color component which still used simple shapes, but used them to make a silly alien in space. Purples, greens and blues were used for this painting project.
Here is the painting that I made with the students that day: