Colours 101 ~ An In Depth theory

The human eye is the most sophisticated ‘device’ on the planet at interpreting colours. The human eye can not only see colours but it can also interpret colours based on the surroundings in which the colours are viewed. There are additive colours and subtractive colours which are the two main theories for explaining the way we are exposed to light and therefore colour. Colour is defined by wavelengths of light that our eye is exposed to.

Additive Colour (RGB)

Additive colour involves light emitted directly from a source or illuminant of some sort, such as the light used to create colours on TV screens, projectors, web, and digital displays like computer monitors and other instances where colour is created by light emitting from a source. It is the colour space associated with Additive colour and thus must be used when designed for mediums in which will be emitted from a source.


Subtractive Colour (CMYK)

Subtractive colour, the mixing of paints and dyes; uses inks colored in cyan, magenta, and yellow to create colour and natural colorants to a range of colours. Each colour is caused by the mixture absorbing some wavelengths of light and reflecting others. The subtractive colour system starts with white light. Coloured films placed between the viewer and the light source or reflective surface such as a white piece of paper, subtract wavelengths form the white and make a colour. The subtractive colour system is the colour space associated with subtractive colour thus must be used when designing for mediums in which ink will be placed on the paper or other substances. So in other words, Ink-jet color printers’ use these four inks because the ink on the paper absorbs color from the light it reflects.



So where is the Black?

The ‘black’ is generated by mixing Cyan, Magenta and Yellow primaries, so four-colour printing uses black ink in addition to the subtractive primaries. A combination of 100% Cyan, magenta, and yellow often results in a muddy dark brown colour that does not quite appear black. Adding black ink absorbs more light, and yields much darker blacks.

Spot Colours

Spot colours are made according to particular specifications in a colour system such as Pantone. A spot colour is one that is not built using process colour inks (cyan, magenta, yellow and black). Instead, the colour is printed using an ink made exclusively for that colour. In spot colour printing, each colour is printed using a separate plate. Spot colour results from adding a specific second colour to the single color. Black is a traditional single colour.

Process Colours

In process colour, four placets are used. A layer of tiny colour dots is printed from each plate, and overlapping dots to create an illusion of solid or graduated colour. The process colours are colours specified in percentages of Cyan, Magenta, Yellow, and Black. The only way to print the continuous tones in a photograph is by using process colours.

Primary colours

Primary colours consist of red, blue, and yellow. (We learnt this in grade school!). Every other colour can be created from them even white and black, but red, blue, and yellow can not be created from other colors.

Secondary colours

These colours are made by mixing two primary colours such as colors red, blue, and yellow to make secondary colours like green by combining blue/yellow, orange by combining red and yellow and violet by combining blue and red and so on. Do you remember mixing these colors in elementary school and experimenting with these colours in art class? Well I bet you didn’t know that you were actually making secondary colours for all those beautiful paintings that you did.

Tertiary colours

These colours are made up by combining equal parts of a primary colour and a secondary colours. There are six tertiary colours red-orange, yellow-orange, blue-green, blue-violet, red violet, yellow green and blue-green. So when we mix the primary colour blue for example, with the secondary colour green, we get the tertiary color ‘blue-green’.