Painting with ice. All you need to do is fill an ice cube tray with liquid water color and water. Stick a strand of tape directly on top of the ice cube tray. This is so the toothpicks will stay in place while freezing.
Ice painting is a fun way to cool off during the hot summer months. This website even has a substitution for children under the age of two who will want to put the ice paint in their mouths: kool-aid ice.