A representation of RGB colour model versus CMYK colour model.

RGB vs. CMYK

The RGB colour model is an additive colour model. Red, Green, and Blue light are added together in various ways to reproduce a broad array of colors. White is the “additive” combination of all primary coloured lights, while black is the absence of light.

The CMYK colour model is a subtractive colour model. Cyan, Magenta, Yellow and blacK inks are combined in printing to “subtract” brightness from a typically white background. White is the absence of ink, while black is the result of a full combination of coloured inks

Examples of RGB devices: (input) colour TVs, video cameras, image scanners, and digital photo cameras, (output) computer monitors, cell phone screens, video projectors

Examples of CMYK devices: (output) colour printers

What does this mean for illustrators?

While we typically create our digital artwork (or make digital adjustments to scanned, physical artwork) in RGB environments, we ultimately output to CMYK printers which have a smaller colour gamut. Due to the many great differences between these two colour reproduction technologies, comparisons between RGB displays and CMYK prints AND conversion from RGB displays to CMYK prints prove difficult.

How do I address this issue when creating digital artwork destined for print?

There is unfortunately no foolproof method of achieving consistent printed colour from artwork created (or adjusted) on the computer. While some may recommend setting your Photoshop image mode to CMYK (“Image > Mode > CMYK Color” in the menu bar) when working, I would instead recommend to work in RGB (“Image > Mode > CMYK Color” in the menu bar) so as to not initially limit your palette. Even though theory clearly tells us that when making colour decisions we should take into account the fact that some RGB colours will be lost in translation to CMYK, given that it is near impossible to accurately identify which colours from our palette do or do not translate, I would try to achieve a satisfying colour harmony on the monitor and then try to achieve colour fidelity by printing proofs.

One of the methods you can use to attempt to preview on a monitor how your artwork will be reproduced on a printer is soft proofing. While from my experience this is not 100% reliable, you may wish to take a look at your artwork with soft proofing to identify the severity of colour variation between profiles. Below, a link to an article on soft proofing:

http://www.zuberphotographics.com/content/printing/soft-proof.htm