You will remember that the quiz question for this week was:
Explain the difference between additive and subtractive colour systems and the difference in where they are used.
In additive colour systems the colours mix like light. So when primary colours mix the add to make white.The RGB colour system used to display colours on a screen is additive. The colours mixed are red, green and blue.
In subtractive systems each colour that mixes is subtracted so by mixing all the primaries we end up with black. The CMYK colour system used in printing is subtractive. The colours mixed are cyan, magenta, yellow and black (Key).