The best way to understand how an LED makes different colors is to go to the PAINT program in Windows. Go to the 'edit colors' tab. Click on the different colors they have on the pallete and look at the combination numbers for Red Green Blue (note that white is max red, max green, and max blue). The higher the number, the more of the color added. Most LED controllers use PWM to control the amount of average current an LED receives, since the simple on/off is the easiest way to control digitally, and you vary the on/off ratio to increase or decrease the average current.