Salt Painting: paint glue lines on dark paper. Sprinkle with salt and let dry. Paint with watercolors or food coloring--the paint will spread thru the glue lines. Experiment mixing colors by dropping one color next to another.
OK you guys, I think I've fallen in love with another kids activity. These crystal stars are awesome! Any activity where I get to make something beautiful from bright rainbow colours, and I'm totally on board!