when color information is encoded digitally, certain frequencies of light are stored using more bits than other frequencies. This is called gamma correction. Gamma correction is performed because the human eye can distinguish smaller differences in some wavelengths than others. By allocating more bits to frequencies with a higher visual Resolution, maximizing detail with minimum wasted bits.
Gamma corrected color is properly noted using the ' symbol, as in Y'U'V' or R'G'B', but generally speaking all color on a computer should be assumed to be gamma corrected unless you have reason to believe otherwise.