If you can get students to understand how color works together, then you can get them to build complex and engaging works of art. Looking for that subtlest of subtle grays? Want to make gray look like blue? Place some orange next to it.
Complementary colors are where its at. If you place colors on opposing sides of the spectrum, they will emphasize one another's chroma, or brightness.
Harmony. If you place colors of similar, but different shades and values next to one another you get rhythm and harmony.
There are lots of things to do with the color spectrum, but you have to be able to visualize the color wheel, Oh, and take risks. After all, these are only art supplies. Maybe you'll learn something while you try capturing that rainbow against a blue sky, or about atmospheric interference.
PS add a light blue to things farthest in the distance.