Little tops have colourful stickers. Rotation of tops gives an optical illusion of colour mixing. The result of mixing red and green is different (yellow), and red and blue is yet another (magenta - pink).

The sensation of seeing almost all colours may be experienced when we mix in certain proportions only three light beams with exactly matched spectrum width.

The word colour comes from Latin. In most contexts it refers to what the eye perceives. The word colour is used to refer to different cards in card games. Colours were used in army for differentiating rank, and nowadays colour are used to label quarks.

Instead of colour, one can say also a paint. For sounds we say "timbre". These names are associated with perception of various stimuli with our eyes (or ears). On the other hand, the colour depends on ingredients forming an object. In particular ingredients with clear, vivid colours are called dyes.

The reception points in our eye register incoming light waves - which are sets of stimuli for our brain. Following further processing in the reception points these stimuli undergo transformation into sensations. Such a transformation does not follow the order of linear way. In other words, the same sensation can be created in our eye as a result of various light wave configurations.

White light can be obtained through mixing only three colours: red, green and blue. If we project these three colours onto a screen so that they cover, what we perceive is white light. By mixing these colours in proper proportions we can obtain a desired light spectrum range. That is why we call red, green and blue basic complementary colours. But if we subtract a colour, like in the print process, we have other three fundamental colours: magenta, yellow and cyan.