Color Facts



  • Colour is the way our eyes see different wavelengths of light. Red light has the longest waves – about 700 nanometres, or nm (billionths of a metre). Violet light has the shortest waves – about 400 nm. Light that is a mixture of every colour, such as sunlight and the light from torches and ordinary lightbulbs, is called white light (see mixing colours).
  • Things are different colours because molecules in their surface reflect and absorb certain wavelengths of light.
  • Deep-blue printers’ inks and bright-red blood are vividly coloured because both have molecules shaped like fourpetalled flowers, with a metal atom at the centre.
  • Iridescence is the shimmering rainbow colours you see flashing every now and then on a peacock’s feathers, a fly’s wings, oil on the water’s surface or a CD.
  • Iridescence can be caused by the way a surface breaks the light into colours like a prism does (see spectrum).
  • Iridescence can also be caused by interference when an object has a thin, transparent surface layer. Light waves reflected from the top surface are slightly out of step with waves reflected from the inner surface, and they interfere.
  • The surface skin of water on some spilt oil interferes with the vibrations of light causing it to be split up into the colours of the spectrum.
  • The macaw gets its brilliant colors because pigment molecules in its feathers soak up certain wavelengths of light and reflect others, including reds, yellows and blues, very strongly.
  • Iridescence on a CD is a result of light waves reflecting from both the top surface and the inner surface. This causes the spectrum of light which is sometimes visible.
  • As a light source gets hotter, so its colour changes from red to yellow to white to blue.