This tutorial is something that can be simple enough for kids or you can tweak it to make it more advanced for an experienced painter. This technique is watercolor resist where you start by drawing your outlines with oil pastels and then use watercolor paint to paint in each area with a different color. The oil keeps the watercolors from traveling into any unwanted areas. This technique also looks quite beautiful if you do all of your lines with a white oil pastel and then paint over it to reveal your outlines. Kind of similar to writing one of those secret messages and revealing it with the little magic marker.
Check out the video tutorial and see how easy this technique is.