Achromatic means without colour. So any object or surface that lacks a distinct hue is said to be achromatic. Pure, saturated, achromatic colours appear black, white and grey but unsaturated, near-neutral colours are also sometimes described as achromatic.

About achromatic colours
  • Saturated colours are colours produced by a single wavelength (or a small band of wavelengths) of light.
  • Unsaturated achromatic hues include browns, tans, pastel tints and equivalent darker tones.
  • When mixing paint, achromatic hues are produced by adding black and/or white until the original colour almost disappears.
  • Achromatic colours are produced on TV, computer and phone screens by mixing RGB colours in equal proportions. The RGB colour model produces a middle grey with the hexadecimal colour value #808080.
  • The way achromatic hues appear to an observer often depends on adjacent more saturated colours. So next to a bright red couch, a grey wall will appear distinctly greenish – green and red being complementary colours.