• Support Guides

    Colour Guide

    In this guide, you'll find clear explanations of RGB and CMYK colour spaces, why CMYK printing is necessary, and expert tips for setting up your artwork files to achieve precise and impressive print outcomes.

    • Comparison RGB
    • RGB
    • Comparison CMYK
    • CMYK

  1. Understanding Colour: RGB vs. CMYK

    RGB and CMYK are two distinct colour models. RGB stands for Red, Green, Blue, while CMYK stands for Cyan, Magenta, Yellow, and Key (Black). The primary difference between these two colour models is the way they create colours.

    • Rgb Theory
    • Cmyk Theory

  1. Colour model:

    • RGB (Red, Green, Blue): An additive model where colours are created by combining light sources. Mixing all three primary colours at full intensity produces white, while the absence of light results in black. This model is ideal for digital displays like TVs, computers, and smartphones.
    • CMYK (Cyan, Magenta, Yellow, Key (Black)): A subtractive model where colours are created by removing wavelengths of light reflected from a white surface. Overlaying all primary colours (CMY) theoretically creates black, but in practice, a dedicated black ink (K) is used for deeper, richer tones. This model reigns supreme in physical printing like brochures, posters, and magazines.

    Gamut:

    • RGB: Boasts a wider gamut, capable of generating a broader spectrum of vibrant and saturated colours, particularly in greens and blues. This is due to the inherent nature of light emission.
    • CMYK: Has a narrower gamut compared to RGB. While still offering a vast array of colours, it may struggle to reproduce the full vibrancy and intensity achievable digitally. This limitation arises from the physical properties of inks and their ability to absorb light.

  1. Why Print in CMYK?

    When it comes to achieving colours in commercial print presses, inks are combined to produce colours on a white background. Typically, cyan, magenta, yellow, and black inks are used, which is why CMYK files are used to prepare artwork for print.

    On the other hand, RGB picture files are ideal for electronic screens and projectors that reproduce coloured images via a light source. However, they are not designed to instruct a printer on how to replicate those colours with inks.

    This is why all RGB files presented for print need to be converted to CMYK. However, because RGB has a wider gamut of colours than CMYK, some hues, especially vivid oranges and greens, may be compromised during conversion.

    • BEFORE (RGB)
    • BEFORE (RGB)
    • AFTER (CMYK)
    • AFTER (CMYK)

  1. It’s better to create images in CMYK from the outset, or convert any RGB files to CMYK yourself if you want to have a more accurate idea of how your design will appear on print.

    Please Note: There is an exception to this! If you are ordering Photo or Fine Art Prints, we will happily accept RGB files.

  1. Converting RGB to CMYK


    There are several ways to convert RGB to CMYK, depending on your needs and preferred tools:

    Software Tools:

    • Image editing software: Most popular image editing software like Adobe Photoshop, GIMP, and Affinity Photo offer built-in conversion options. Typically, you can find the conversion option under the "Image" or "Edit" menu. Be mindful of the specific conversion profile used, as different profiles can produce slightly different results.
    • Online converters: Several online websites offer free RGB to CMYK conversion tools. These are convenient for quick conversions but may not offer the same level of control and accuracy as dedicated software.
    • Design software: Many design applications like Adobe Illustrator and InDesign also allow you to convert colours between RGB and CMYK directly within the program.
    • BEFORE CONVERSION
    • BEFORE CONVERSION
    • AFTER CONVERSION
    • AFTER CONVERSION
    • AFTER ADJUSTMENT
    • AFTER ADJUSTMENT

  1. Considerations:

    • Colour accuracy: Remember that CMYK has a narrower gamut than RGB, so some colours may not translate perfectly. Pay attention to the "out of gamut" warnings in software and consider adjusting your design accordingly.
    • Conversion profiles: Different conversion profiles can affect the final output. Consult with your printing company or choose a profile based on the specific printing press or paper used.
    • Preview limitations: On-screen previews of CMYK colours may not accurately reflect the final printed result due to differences in screen calibration and printing processes.

  2. Summary

    Regardless of whether you submit your artwork as an RGB or CMYK file, all files will be converted to CMYK before going to print. So if you want to be sure your colours will be accurately represented on the finished article, we recommend you convert your file to CMYK and view it on a high-quality monitor prior to submission, or request a printed proof from our Customer Service Team. For more info on making sure your files are print-ready, read our guide to supplying artwork.

    Please note: if you’re printing onto Kraft paper, the underlying brown background will affect how coloured inks appear on the final product.