Using Colour Correctly

Using color for better printed results

A lot of print data we receive uses the wrong colour mode for perfect offset print results. Below is a brief explanation of RGB and CMYK, differences between the two and when you should use which one.

What is RGB?

All colors of the RGB colour model are created with the 3 primary colors Red, Green and Blue. Mixing these light primaries equals white. This additive colour method can display a very wide range of colors.

Every monitor displays colors in RGB mode – depending on the monitor some do better and others worse. When you create something for a screen display, such as a website or web pages, you should create your file in RGB mode.

Multiple factors influence the quality of colour depiction on a monitor, e.g. colour depth (also depending on the graphics chip), age, quality, colour temperature, display type and last but not least lighting conditions in rooms and the angle of view. Some of this can be minimized by monitor calibration.

Compared to the CMYK colour palette, the RGB color model is very wide but it also has some drawbacks. The yellow color spectrum doesn’t provide as much different colors as other color palettes. Blue and purple color ranges in turn are much more varied in RGB. Metallic colors like silver or gold as well as differences between matte and glossy can’t be displayed with RGB, which makes it not the best choice for printing.

What is CMYK?

The primary colours of the CMYK colour model are Cyan, Magenta, Yellow and black (black, Key). CMYK colors are added on top of each other. The more color (cyan, magenta, yellow) you add the less light is reflected. As you basically take away brightness you call this a subtractive colour model.

The CMYK colour model is what is used for printing.

Why do colors change when exporting RGB to CMYK?

TheCMYK color range is a lot smaller than RGB. When you convert a larger color model to a smaller one some colors, especially the bright and shiny ones, go "missing". The other way around (scanning printed images) causes less issues as the target color model is bigger and most color ranges can be accommodated.

Due to this effect most designers set up the color model before working on the artwork.  For example, if you know you want a leaflet printed, then with CMYK right away.