Use duct tape for words. Place crayons on top. Blow dry on high heat till crayons melt. Blow dry side to side to blend colors. Slowly remove duct tape to reveal words. I've seen the crayon thing before, but love the duct tape idea!
Black glue / watercolor art - mix a few blobs black acrylic craft paint into a bottle of Elmer's Glue-All white school glue - draw with glue on water color paper, let dry 1 day - color with water colors