Bands of colour

An observer perceives bands of colour because:

  • Colour is not a property of electromagnetic radiation, but a feature of visual perception.
  • It is the human brain that draws lines between different bands of colour when an observer looks at a rainbow for example.
  • A human observer can distinguish between colours corresponding with many thousands of single wavelengths of light in the visible spectrum. These colours are called spectral colours.
  • Combinations of wavelengths from different areas of the visible spectrum produce other colours when perceived by a human observer which are called non-spectral colours.
  • There is no property belonging to electromagnetic radiation that causes bands of colour to appear to an observer. The fact that we do see distinct bands is often described as an artefact of human colour vision.
  • The visible spectrum is formed of a smooth and continuous range of wavelengths that can be demonstrated to produce a smooth and continuous range of colours.
  • Cone cells in our eyes are particularly sensitive to red, green and blue wavelengths.
  • Our brains process information received from the eye to produce all the colours of the visible spectrum.

https://en.wikipedia.org/wiki/Rainbow