Related Article: Working of Light Emitting Diode (LED)
One commonly used schematic symbol for these LEDs is shown below.
Working of Multicolor RGB LEDs
Multicolor RGB LEDs actually contain two PN junctions that are connected in reverse-parallel i.e. they are in parallel with the anode of one being connected to the cathode of the other.
If a positive potential is applied to the terminal as shown below, the PN junction on the left will light.
Note that the device current passes through the left PN junction.
If the polarity of the voltage source is reversed as shown in the figure below, the PN junction on the right will light.