If you’re not a professional designer, and you intend to print something that you designed on your computer, it is important to understand the difference between RGB and CMYK color modes and when you should or shouldn’t use them. Without that basic understanding, the chances are quite good that what you see on your monitor will not be what comes out of your printer.

Let’s first look at the differences between RGB and CMYK. There are other color modes out there, too, but these two are – by far – the most prevalent. Fair warning – this can be a bit confusing.

RGB stands for the three primary colors – Red, Green and Blue. Precise combinations of these three colors can be added to one another to create just about every other color. As such, we refer to R, G & B as additive colors. For example, if you wanted to create a shade of yellow, you would simply combine predetermined amounts of green and red.

Here’s the confusing bit – the more these three colors balance each other out, the lighter the resulting color becomes. And when you combine all three RGB colors in equal amounts, you end up with the color white – the purest combination. Unlike CMYK, which we’ll look at in a moment, RGB colors tend to neutralize each other instead of build on each other.

RGB is the color mode that is usually associated with computer monitors, other displays, digital cameras and scanners. RGB works the same way on both computer monitors and within your printer.

CMYK works with four non-primary colors – Cyan, Magenta, Yellow and Key (better known as black), rather than three primary colors. Each of these four colors are complex combinations of primary and other colors.

CMYK works in an entirely different way than RGB. Where RGB uses additive types of primary colors, CMYK uses subtractive colors. Since C, M, Y and K are already complex colors, what you’re actually doing is removing some of the complexity from them in order to obtain other colors. For example, if you add magenta to yellow, what you’re actually doing is subtracting the yellow from magenta. As the magenta loses its yellow component, you end up with a bright red color.

CMYK colors act much like regular paint in that the more you add together, the darker the result will be. Technically, what is happening is that when more colors are involved, more light gets absorbed. If you add cyan, magenta and yellow together, you end up with a dark brown color. When you add the ‘key’ color – black – the full amount of color and light is removed from the image.

CMYK is used less often than RGB because many home printers are actually able to print using the full RGB spectrum. However, CMYK is often employed by professional printing companies because they are able to achieve highly precise color matches that, in some cases, might not be able to be achieved with RGB.

When to Use Them
One of the most common printing mistakes arises from the misuse of the color modes.

If you’re using one of the more popular applications – such as Photoshop – to create your design, you will notice that it automatically defaults to the RGB color mode. This is because Photoshop and most other image-editing applications are mainly used for website design, image editing and various other forms of media that usually end up on a computer screen. CMYK output is possible, but you will have to manually override the RGB setting.

In order to achieve the expected results, the printing method must match the output method. If an RGB design is printed using a CMYK printing process, the colors appear differently because the printer is not able to comprehend the color combination instructions. It’s like speaking one language when your audience is expecting another. This means that although a design might look absolutely perfect when viewed on your computer monitor, there will be distinct differences in color between the on-screen version and the printed version. If you’ve created your designs in the RGB color mode and intend to have them professionally printed, you will need to remember to convert the design to CMYK before sending it off. This function is usually automated in today’s design programs.

The physics of color combination and light absorption are obviously much more complicated than we’ve discussed here. Entire books have been written about them. However, for most people, the basic rule of thumb is to create and output your design in RGB color mode if it will only be used digitally (online). If you plan on printing your design, and especially if you plan to have it professionally printed, you should create and output your design in CMYK color mode.

Return to the Tech Trends Newsletter