RC4 dimmers are often used to control color temperature of LED motion picture lighting.  This is done by combining cool-white and warm-white light sources.  When only the cool LEDs are on the color temperature value is highest (around 7000 Kelvin); when only the warm LEDs are on, the color temperature value is lowest (around 3000 Kelvin).  If both sources are mixed equally, the color temperature is in the middle (around 5000 kelvin).  It’s important that the total light output (measured in Lumens) is always the same.  RC4 Series 3 dimmers provide cross fade mode for this purpose.