MAGIC! I've been doing this all over my carpet, it works on old stains, new stains-- basically EVERYTHING!
As anybody with kids can tell you, Kool-Aid spills are inevitable, especially on white carpet. Many conventional carpet cleaners won't pull up the colorful mess, but a combination of quick action, club soda and a homemade cleanser of water and ammonia lifts even the brightest Kool-Aid flavor.
Also on these boards
Iron Stains out of carpet