Colour

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