Colour is a crucial part of graphic design today, but it is something that consumers, clients and designers take for granted. Colour can bring a design to life, help to establish hierarchies, highlight key information and add pace and emotion to a design. However, it is a design aspect that is easy to get wrong and causes problems when a job prints incorrectly.

Colour control is one of the primary tasks that a graphic designer is responsible for in the print production process. This is achieved through colour management, a process that governs how colour is translated from one piece of equipment to another (for instance, from digital camera to a computer to the printing press), ensuring accurate and predictable colour reproduction. Colour management is needed because each device responds to and produces colour differently.

Colour spaces

Designers can work with different colour spaces – systems that define the hue, saturation and value of a colour in the different design and printing processes. Colour spaces include RGB (red, green, blue) and CMYK (cyan, magenta, yellow and black), which are used by colour monitors and the four-colour printing process.

RGB/CMYK

A colour is made up of different quantities of red, green and blue light, which can be presented as a ratio. These ratios produce different results in different colour spaces. RGB is the additive primary colour space that computer monitors use and CMYK is the subtractive primary colour space used in the four-colour printing process. In order to achieve accurate and reliable colour reproduction, it is necessary to know how the different devices in the design and print production system use colour. Red, green and blue (RGB) are the additive primaries that form white light, and they are used to produce colour images on a computer screen. The RGB colour space that computer monitors use can reproduce about 70 per cent of the colours of the spectral gamut that can be perceived by the human eye. Cyan, magenta, yellow and black (CMYK) are the subtractive primaries used in the four-colour printing process where each represents one of the print colours. Computer images in the RGB colour space are converted to the CYMK colour space for printing.

Each subtractive primary is formed from two of the additive primary colours as shown above. Where two subtractive primaries overlap, they create an additive primary colour.

Additive primary colours represent a component of white light. Where two additive primaries overlap, they create a subtractive primary colour.

Describing colour

Colour can be described according to three features: its hue or colour; its saturation or chroma; and its value or brightness.

Hue refers to the unique characteristic of a colour that helps us visually distinguish one colour from another. Hues or colours are formed by different wavelengths of light.

Saturation or chroma refers to the purity of a colour and saturation levels describe a colour’s tendency to move towards or away from grey.

Brightness or value refers to how light or dark a colour is. Changes in the brightness value can be achieved by mixing a colour with black or white.