In this article you can read about working with RGB LED diode. You can display 8 colors using one LED diode. LED is connected by 3 pins to MCU for control color and by 1 pin is connected to MCU via transistor to regulate brightness (see scheme). Regulation of brightness is performed by PWM.
This is simple illustration how to build easy PWM LED control with IQRF TR module and a few other components. Continue reading