Learning your colours

Thursday 15 January 2015

There are two commonly-used systems for specifying colour in the design and printing industries – CMYK and PMS. You will probably hear your designer or printer refer to these colour specifications, but what do they mean?

A venn diagram showing cyan, magenta and yellow combined

CMYK, or four-colour process, uses cyan, magenta, yellow and key (black) inks. These primary ink colours (excluding black) are transparent, allowing them to be applied on top of one another in various densities to create the secondary colours of red, green and blue.

In commercial printing the four inks are overlaid in sequence each in their own pattern of very fine dots known as a screen. The eye optically ‘mixes’ these dots of varying colour, creating the appearance of a range of colours.

An image showing the cumulative effect of printing cyan, magenta, yellow and black inks

From left to right: cyan; cyan & magenta; cyan, magenta & yellow; and cyan, magenta, yellow & black

The combination of cyan, magenta, yellow and black allows you to create a huge range of colours, however, accurately specifying the appearance of the final colour can be difficult. In 1963 Lawrence Herbert came up with a solution to this problem by creating a new system, which he called the Pantone Matching System (PMS). The system provides a book of standardized colours which both printers and clients can refer to. Each colour has a unique reference number, and printers can either use ready-mixed colours, follow the formula provided for mixing the desired colour using Pantone’s 14 mixing inks, or create a close equivalent by using a formula for CMYK printing. Today Pantone offers designers and printers a range of 1,677 solid (or PMS) colours, and formulas for mixing 2,868 colours.

What does this mean for me?

Because CMYK inks are laid down one after the other, up to four separate printing plates are required to build up the final colour, and this can be more expensive than necessary. If a design uses a very limited (fewer than four) palette of colours it may be preferable to use spot colours since each colour is premixed, and therefore only requires one plate to print it.

Spot colours also bring other benefits, such as an increased intensity of colour, assured accuracy of colour, and the ability to print some shades which CMYK cannot. However, spot colours become expensive when they are used alongside CMYK inks as they require an additional plate of their own, and depending upon the printing press, this may require a second pass through the press.

It’s well worth understanding the implications of any colour choices early on in the design process to help you get the best value for money and avoid unexpected costs later on.