Rainbow colour

Rainbow colour refers to the colours seen in rainbows and other situations where visible light separates into its component wavelengths and the corresponding hues become visible to the human eye.

  • Rainbow colour (also called spectral colour) is a colour model.
  • A colour model is a theory of colour that establishes terms, definitions, rules and conventions for understanding and describing colours and their relationships with one another.
  • A spectral colour is a colour evoked in normal human vision by a single wavelength of visible light (or by a narrow spread of adjacent wavelengths).
  • When all the spectral colours are mixed together in equal amounts and at equal intensities, they produce white light.
  • In order of wavelength, the rainbow colours (ROYGBV) are red (longest visible wavelength), orange, yellow, green, blue and violet (shortest visible wavelength).
  • It is the sensitivity of the human eye to this small part of the electromagnetic spectrum that results in our perception of colour.
  • Whilst the visible spectrum and its spectral colours are determined by wavelength (and corresponding frequency), it is our eyes and brains that interpret these differences in electromagnetic radiation and produce colour perceptions.
  • Naming rainbow colours is a matter more closely related to the relationship between perception and language than anything to do with physics or optics.
  • Even commonplace colour names associated with rainbows such as yellow or blue defy easy definition. These names are concepts related to subjective impressions.
  • Modern portrayals of rainbows show six colours – ROYGBV. This leaves out other colours such as cyan and indigo.
  • Atmospheric rainbows actually contain millions of spectral colours. Measured in nanometres there are around 400 colours between red and violet, measured in picometres there are 400,000.