What are CMYK, Pantone and RGB?

CMYK stands for cyan, magenta, yellow and black: the four ‘process’ colours that commercial printers use to reproduce the illusion of continuous-tone full colour. Using these four coloured inks it is possible to create a wide variety (or ‘gamut’) of colours on paper – known as ‘subtractive’ colour.

However this is a limited process and sometimes it will be unable to accurately reproduce some images. On occasion the work can be be supplemented by two more colours – a green and an orange – to create a six colour proprietary system from Pantone known as Hexachrome™. Green and orange are added as these are difficult colours to reproduce accurately using just the four process colours.

Note: K for black? Why is it not CMYB?
The K in CMYK stands for key, which is derived from the printing term ‘key line’, widely used prior to digital age, when key lines were drawn onto artwork by hand and printers then ordered to fill these spaces with colour or image.

If specific colours are needed in a printed work, it may be appropriate to use ‘spot’ colour rather than the CMYK of ‘process’ colour. The most commonly used spot colour matching system is called Pantone. The Pantone company has established a standard for spot colours and produce a range of swatch materials. The important distinction between CMYK and spot colour is that whereas with CMYK a particular colour is reproduced as near as possible by mixing together dots of cyan, magenta, yellow and black, a spot colour is a solid colour, no dots, no mixing, no illusion – as someone once said: it does exactly what it says on the tin! This means that there is a much wider range of colour available to the designer, and that the printer and designer can work from the same reference material, ensuring consistency between artwork and printed job.

RGB stands for red, green and blue, a system of ‘additive’ colour used in TV screens and computer monitors. As with CMYK, the RGB system relies on mixing coloured dots to give the impression of something being full colour. The big difference is that CMYK does it with ink and RGB does it with light. It’s not possible to print with light, so it is not possible for commercial printers to accept artwork with any elements using the RGB colour system.

When on screen, even artwork being made using CMYK is represented using RGB (it’s the way that all monitors work). This means that reds, greens and blues can appear stronger than they will appear in print.