Achromatic means without colour so refers to surfaces or objects that appear white, grey or black. Achromatic colours can be described in terms of their apparent brightness but are without hue or saturation.

  • Near-neutral colours such as tints or dark tones are achromatic.
  • The lightest shades of pastel colours are almost achromatic.
  • Deep shadows and the world as it appears in darkness are almost achromatic.
  • When mixing paint, achromatic hues are produced by adding black and/or white until the original colour almost disappears.
  • Achromatic colours are produced on digital screens by mixing red, green and blue light in equal proportions. The RGB colour model produces achromatic hues when all three components of a colour have the same value. So the RGB colour values R = 128, G = 128, B = 128 together produce a middle grey.
  • 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.