I love the book Old Black Fly (cick to see a preview on Amazon's website) by Jim Aylesworth with illustrations by Stephen Gammel. This year my 3rd graders drew Old Black Fly with crayons and we decided to add paint splatters to mimic the illustrations in the book. Most colors look super cool splattered on the artwork.
Red, however, looks like blood. Still cool, but could be a little gruesome. Next time we'll substitute another color choice! :)