colors (was Re: [pygame] "Making Games with Python & Pygame" free book)

[Miriam English <mim@xxxxxxxxxxxxxxxxxx>]

Sorry, I said I would show an example of how subtractive color mixing 
works after I gave a wrong example. So, just very briefly...

It helps to see a rough color circle. So you can see opposites.
  R
Y   P
G   B
  C

R = red
Y = yellow
P = purple
G = green
B = blue
C = cyan

When painters mix cyan + yellow they get green.
The paints or inks filter out colors.
So look on the other side of the wheel to find the opposite.
  cyan = -red
  yellow = -blue

the white paper reflects all colors
  white = red + green + blue

cyan + yellow = white - red - blue
              = red + green + blue - red - blue
              = green