What You Need to Know About the CMYK Color Model

CMYK is Essential to Accurate Colors in Printing

CMYK Color

The CMYK color model is used in the printing process. It is used in your office inkjet and laser printers as well as the machines used by professional commercial printers. As a graphic designer, it is essential that you understand both the CMYK and RGB color models and when you will need to use them. 

How RGB Leads to CMYK

To understand the CMYK color model, it is best to start with an understanding of RGB color.

The RGB color model is made up of red, green and blue. It is used on your computer monitor and is what you will view your projects in while still on the screen. RGB is retained for projects that are designed to stay on screen (websites, pdfs, and other web graphics, for instance). 

These colors, however, can only be viewed with natural or produced light, such as in the computer monitor, and not on a printed page. This is where CMYK comes in.

When two RGB colors are mixed equally they produce the colors of the CMYK model, which are known as subtractive primaries.

  • Green and blue create cyan (C).
  • Red and blue create magenta (M).
  • Red and green create yellow (Y).
  • Black is added to the model because it cannot be created with the 3 subtractive primaries (when combined they create a dark brown). The K, or “key,” stands for black.

CMYK in the Printing Process

The four-color printing process uses four printing plates; one for cyan, one for magenta, one for yellow, and one for black.

When the colors are combined on paper (they are actually printed as small dots), the human eye sees the final image.

CMYK in Graphic Design

Graphic designers have to deal with the issue of seeing their work on screen in RGB, although their final printed piece will be in CMYK. Digital files should be converted to CMYK before sending them to printers unless otherwise specified.

This issue means that it is important to use “swatches” when designing if exact color matching is important. For instance, a company's logo and branding material may use a very specific color such a 'John Deere green.' It is a very recognizable color and the most subtle of shifts in it will be recognizable, even to the average consumer.

Swatches provide a designer and client with a printed example of what a color will look like on paper. A selected swatch color can then be chosen in Photoshop (or a similar program) to ensure the desired results. Even though the on-screen color won’t exactly match the swatch, you know what your final color will look like.

You can also get a “proof” (an example of the printed piece) from a printer before the entire job is run. This may delay production, but will ensure exact color matches.

Why Work in RGB and Convert to CMYK?

The question often comes up as to why you simply wouldn't work in CMYK while designing a piece destined for print. You certainly can, but you will need to rely on those swatches rather than what you see on the screen because your monitor uses RGB.

Another issue you may run into is that some programs such as Photoshop will limit functions of CMYK images.

This is because the program is designed for photography which uses RGB.

Design programs like InDesign and Illustrator (both Adobe programs as well) default to CMYK because they are designed for designers. For these reasons, graphic designers often use Photoshop for photographic elements then take those images into a dedicated design program for layouts.

David Bann. “The All New Print Production Handbook.” Watson-Guptill Publications. 2006.