Visible Color Spectrum

The LED chip-making process is complex and delicate. LED "chips" are crystal wafers grown in specialized laboratories, and are made from various semiconductor materials to produce different wavelengths (colors), or combined to produce broad spectrum "white light." The semiconductors materials most typically used are Indium gallium nitride (InGaN), Aluminum indium gallium phosphide (AlInGaP), aluminum gallium arsenide (AlGaAs), Gallium arsenide phosphide (GaAsP), and Gallium (III) phosphide (GaP). 
The visible color of light is determined by the wavelength, measured in nanometers ("nm"). Visible light is a small range (within the large electromagnetic spectrum) that is visible to the human eye (typically 390-750 nm). The electromagnetic spectrum is composed of different forms of radiation, from Gamma-rays (short wavelengths, high frequency, high energy) all the way to Radio-waves (long wavelength, low frequency, low energy).