Why does a mixture of normal colours make brown.. but the colours of the spectrum together makes white??? Thankyou

Question: Why does a mixture of normal colours make brown.. but the colours of the spectrum together makes white??? Thankyou
- Keywords:
  brown,
  colour,
  spectrum,
  white
Asked by sparks to Asif, Laura, Lena, Sean, Viv on 15 Mar 2012.
- Sean Murphy answered on 14 Mar 2012:
  
  When you mix things like paints, the color you see is what is left over after white light is absorbed by the paint. For example, a blue paint looks blue because the paint absorbs all of the other colours. On the other hand, when you mix different colours of light, they add together to give a complete spectrum, which appears white.
- Laura Waters answered on 15 Mar 2012:
  
  If you mix paint it will always end up a horrible brown colour, that is true!
  Like Sean says, the whole spectrum would give white instead.

Question: Why does a mixture of normal colours make brown.. but the colours of the spectrum together makes white??? Thankyou