colour contrast is another part of the colour theory as used in the interior design area (probably other fields too, but I got to know them via that course. yep, noding my homework).
As a brief reference, the socalled colour wheel:

     YO         YG
  orange          green
OR                   BG
  red              blue
     RP         BP

These are the 8 colour contrasts:
- Achromatic; using the colours black, greys and white. Ok, white contains all colours, but meant is, that you don't see what is generally called a colour.
- Hue; means the pure colours like combining red and blue.
- Light and dark; e.g. a light yellow combined with a dark purple, the divider is chroma (see also the Munsell system).
- Temperature; there are "warm" and "cold" colours, which has to do with the psychology of colours, aka what and how you feel in a red room will be different from the feeling in a blue-dominated room. Imagine a vertical line from yellow to purple: the colours on the left are considered warm, and the right cold.
- Complemetary; two colours diametrically opposite in the colour wheel.
- Simultaneous; the effects of combining greys with a colour.
- Saturation; the contrast of a pure colour with its diluted form (diluted with white, grey and/or black).
- Extension; this is the most vague term and deals with the "visual balance". (use your imagination, that was sort of the summary of my teacher.)

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