Fritzing Creator Kit - #07 Night Light
An RGB LED is an LED package in which three LEDs (red, green and blue) are embedded. They share one common leg. The shared leg in the kit's RGB LED is the cathode (negative). The three remaining leads (anodes) are each assigned one colour. Each built-in LED requires its own series resistor.
For a good colour combination, wrap a piece of white paper around the LED, or stick it into a ping pong ball (drill a 5mm hole).