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Colour Basics
The human eye and light of the 
visible spectrum in any state, are the two agents that allow us to recognise colours. They are responsible for colour appearance. In other words: Our light-sensitive receptors on the retina pass those light impulses from the rods and cones to our brain where they are bundled into a picture. Which colours we specifically identify is dependant on the characteristics
of each individuals’ visual system.
The matter of colour perception allowed man to set up theories about how colour works and can be ordered, and we will point out the most significant components in this learning unit.
A colour circle, based on red, yellow and blue has long been traditional in the field of art. Besides Goethe, who concentrated
on the theory of colours in the philosophy of natural science, Sir Isaac Newton - from a mathematical and physical point of
view - developed the first circular diagram of colours in 1666. This colour wheel is a 2-D description. It shows the purely
saturated, spectral colours of the visual spectrum. The colours between red and blue, including purple, that are not covered in the spectrum, can be seen as an overlap of the
two ends of the spectrum.
The ability to measure and define colours is most important if preparing the map for printing. All visible colours can be described via this 3 parameters:
- Hue
- Brightness or lightness or Value
- Saturation
These characteristics may firstly be illustrated with a 2-D colour model:
Relief: reproduced with the permission of swisstopo (BA027224)
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