Here is a super fun DIY game I came across.  This year, take the kids outside and play this match-up game created by Valerie at Inner Child Fun.  Simply take a rainbow of paint chip cards, punch a shape out of each shade, and also a hole for the ring.  Now the kids can run around and explore nature in all its colorful beauty.  You could make this into a competitive game with prizes at the end, or keep it relaxed and let the kids stop to smell the roses.  What a great activity for Earth Day (or any day)!