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Colour Theories

Subtractive theory (pigment theory)

  • Deals with how white light is absorbed and reflected off coloured surfaces
  • As coloured compounds interact, they subtract colour from the incoming light
  • Rules:
    • Black absorbs the most light
    • White reflects the most light
    • Coloured pigments (natural sources) and dyes (synthetic sources) absorb light and only reflect the frequency of the pigment colour
    • All other colours are absorbed and are subtracted from the incoming light
    • Primary colours
      • Cyan (C)
      • Magenta (M)
      • Yellow (Y)
      • Black (K)

Additive theory (light theory)

  • Deals with radiated light
  • As coloured compounds radiate different wavelengths, the colours add together
  • Rules:
    • Black radiates no light
    • White (sun) radiates all light
    • Primary colours:
      • Red (R)
      • Green (G)
      • Blue (B)
  • The primary colours add to give white

Solution colour

When a compound in solution absorbs light, the resulting colour will be the opposite on the colour wheel