RGB LEDs make use of red, green, and blue semiconductor chips with no phosphor coating.  RGB lighting systems usually combine the red, green, and blue wavelength light produced by these chips to make white light.  RGB LED products can combine the light created by these three chip colors to produce millions of different hues of light.  A single LED chip can only produce a single wavelength of pure color and cannot produce colors containing multiple wavelengths (such as white, brown, or pink) by itself.