This slide shows how the three primary colors may be combined to produce a new color. All three primary colors are switched on-and-off, at the same rate, but each individual primary color is turned on for a different length of time.  The rate at which the primary colors are switched on-and-off is known as the LED output frequency and the percentage of time that each individual output is turned on is known as the duty cycle. First, to perform color mixing, the LED output frequency must be greater than 80Hz. Second, the brightness of each primary color is controlled with the duty cycle of the LED output.  If the desired brightness is 100%, then the output is on all the time. If the desired brightness is 0%, then the output is turned off all the time. If the desired brightness is 25%, then the output is turned on only for one-quarter of the time and turned off for the remaining three-quarters of the time. The result is that the human eye will see the sum of the primary colors’ average brightness.