1. Three legged dual color LED. This type of lamp has three legs, with the middle leg being a common pole, and the two legs on either side being a straight leg and a diagonal leg, each corresponding to a color. Give an example of red green dual color co positivity. Generally, the straight foot corresponds to red, and the diagonal foot corresponds to green. When the current flows from the middle foot to the straight foot, the red light works; When the current flows from the middle foot to the diagonal foot, the green light works; When the current flows from the middle foot to both the straight and diagonal feet simultaneously, the red and green lights work simultaneously, blending into yellow. A typical circuit would choose the red and green colors of this dual color LED to indicate the two working states of the circuit. A special one may require a third mixed color, but the consistency of this mixed color is difficult to grasp. 2. Four legged dual color. This dual color LED is composed of two circuits, one on the left and the other on the right, to drive the two colors separately to indicate the working status of the two circuits. 3. Two colored legs. This dual color LED is also called a bidirectional LED. This dual color LED cleverly utilizes the volt ampere characteristics of light-emitting diodes. Give an example of a red green bidirectional LED. This type of lamp has only two legs, one long and one short. The P pole of the red LED, which is the positive pole welded to the long leg, and the N pole, which is the negative pole welded to the short leg; The P pole of the green LED is soldered to the short leg, and the N pole is soldered to the long leg; When the current flows from the long foot to the short foot, the red light works normally, while the green light does not work because it does not conduct electricity in the opposite direction; When the current flows from the short foot to the long foot, the green light works normally and the red light does not work, thus achieving control of the current flow to control the red and green colors.