What You Need to Know About the CMYK Color Model

The CMYK color model — named after the four base colors of the model: cyan, magenta, yellow, and black — dominates the commercial printing world and in many home-office color printers.

How RGB Leads to CMYK

To understand the CMYK color model, let's start with a review 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 it's still on the screen. RGB is retained for projects that are designed to stay on screen (websites, online documents, and other web graphics, for example). 

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.
• Red and blue create magenta.
• Red and green create yellow.
• 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 composite image.

CMYK in Graphic Design

Graphic designers must 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 commercial printers unless the print shop requests something else.

RGB and CMYK colors are close, but not perfectly identical. Therefore, use swatches when you're designing if exact color matching is important. For example, 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 step may delay production but will ensure exact color matches.

Why Work in RGB and Convert to CMYK?

So why wouldn't you simply 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 is only capable of displaying images in RGB.

Furthermore, some programs including Photoshop limit what you can do to CMYK images. This barrier 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 optimized for print designers. For these reasons, graphic designers often use Photoshop for photographic elements then import those images into a dedicated design program for layouts.