kindergarten color wheel umbrellas with fingerprint rain. Not sure what kind of colour wheel this is, but I like the concept. I find it helps for future concepts to always have the complementary colour directly across from it's mate.
Group art project: Each student designs his/her own piece of the puzzle. This would also be cool to do with the girls, each year on their birthday design a different piece and they get the puzzle for graduation
Watercolour triangles let students paint paper with watercolors, wet on wet, similar colors. Let dry and cut into triangles. Students pick triangles and glue down randomly, leaving white around each one. Maybe try with black or other color background?