 Bi-color and tri-color light emitting diodes, or LEDs, light up in a particular color depending on current flow direction. The basic bi-color LED has two terminals, and the LEDs are connected back-to-back, anode to cathode. The terminal that is made positive determines the LED that lights. If a positive voltage is supplied to the green anode, then the green LED lights. If positive voltage is supplied to the red anode, then the red LED lights. With the two terminal system, only one LED can light at a time, limiting the device to only two colors. In the three terminal LED, the LEDs share a grounding cathode. Like the bi-color LED, a positive voltage connected to an anode lights the LED. When the wire connected to the green anode gets a positive voltage, the light turns green. When the wire connected to the red anode gets a positive voltage, the light turns red. However, because the two anodes are wired separately, it is possible to apply positive voltage to both wires. In this case, the LED gives off a third color, a mixture of the two. This color is often an amber color.