The color characteristic of light possessing a wavelength between 450 and 500 nanometers, located on the spectrum between green and violet. Blue is one of the three primary colors of light. (See Additive Color Primaries.)
In process color printing, blue is also a secondary color produced by the overprinting of cyan and magenta inks. Blue is often—though somewhat incorrectly—used synonymously with cyan. (See Subtractive Color Primaries.)