LEDs give off monochromatic light at a frequency determined by the semiconductor material. An RGB LED (Red-Green-Blue) combines LEDs of the three primary colours to give a full colour spectrum.
Figure 1. An RGB LED in a 5mm package. Note one lead per LED anode and a common lead for the cathodes.Figure 2. By cross-fading the colours an RGB LED can generate a wide color spectrum by mixing light.
