Colour with a system
Colour systems organise the multitude of colours into mathematical or geometrical systems. Often they are classified according to purpose, for example in order to mix colours from an artist's palette or to define colour impressions clearly in a mathematical way. However, there is no such thing as "the one correct system".
There are two classes of colour systems:
Additive colour mixing (e.g. light):
the sum of all colours is white (Newton, CIE-standard system)
Subtractive colour mixing (e.g. paint colours):
the sum of all colours is black (Leonardo, Runge, Klee, Itten, NCS)
Goethe's colour wheel or colour circle contrasts colours with their respective complementary colours. In addition, Goethe studied how colours affect the human consciousness and feelings. He strived to determine the "moral-sensual effect" of the individual colours.
Here, you can find more details concerning the psychological effects and perception of colours: Colour Effects