What is the Bi-color LED?

The Bi-color LED is a handy little component that allows two colors (red and green) in a single LED while only having two pins (cathode and anode), we also name it as dual color LED. The color of the LED depends on the polarity of the connection only allowing one color at a time. Similar LED's that provide two or even three colors usually have three or four pins allowing for a wide range of mixed colors. One would think having two pins is a disadvantage; not so. This Bi-color LED Lamps can easily be applied to a circuit to visually indicate polarity direction. Or in my case it can save me an extra i/o pin on a forthcoming arduino project.

This is a 3 pins bi-color LED.

Of course we can also produce some other dual color LED(Bi-color LED) with just two pins. 

The first thing you'll notice is that this looks like any other common LED, but with a white diffused lens. It has a short negative lead (cathode), and a long positive lead (anode). On the inside there are two LED's in parallel to each other, one forward and one reverse.