Here's a simple little color project that Lou brought home from school this week. It's the same thing I did with my kids too; we all do the same craft. He said his teachers followed it up with Little Yellow and Little Blue by Leo Lionni, which was perfect.
The kids did a print of each colored hand then rubbed their hands together to get a new color. All of my kiddos like the blending part. I think this would be a great way to teach any primary color blending to make the secondary color.