1. What is CMYK? Understanding the Basics of Print Colour Models

    If you've ever submitted artwork for print and been surprised by how different the colours looked on paper compared to your screen, there's a very specific reason for that — and it comes down to the difference between CMYK and RGB. Understanding how CMYK works is one of the most important foundations of print design, and getting it right from the start saves a lot of frustration and reprinting.

    In this guide, we explain what CMYK is, how it works, how it differs from RGB and exactly what you need to do to ensure your printed colours are accurate and consistent.

    What Does CMYK Stand For?

    CMYK stands for the four ink colours used in commercial colour printing:

    • Cyan (C) — a bright blue-green
    • Magenta (M) — a warm pinkish-red
    • Yellow (Y) — a bright primary yellow
    • Key (K) — black, used for depth, shadow and sharp text

    By combining these four inks in varying percentages, commercial printers can reproduce a very wide range of colours on paper. The "K" stands for "Key" rather than "Black" because in traditional printing, black was the key plate to which the other colour plates were aligned.

    How Does CMYK Work?

    CMYK is a subtractive colour model. When ink is applied to white paper, each ink absorbs (subtracts) certain wavelengths of light and reflects the rest back to the viewer's eye. The combination of absorbed and reflected wavelengths is what we perceive as colour.

    For example:

    • Cyan ink absorbs red light and reflects blue and green
    • Magenta ink absorbs green light and reflects red and blue
    • Yellow ink absorbs blue light and reflects red and green

    By layering different percentages of these four inks on top of each other, the printer builds up the full range of colours in the design. This is why CMYK is described as subtractive — colour is created by removing light rather than adding it.

    CMYK vs RGB: What's the Difference?

    RGB stands for Red, Green and Blue — the colour model used by all digital screens. RGB is an additive colour model: screens create colour by emitting combinations of red, green and blue light. The more light is added, the brighter the result — combine all three at full intensity and you get white.

    The key differences between CMYK and RGB for print designers are:

    • RGB has a wider colour gamut — screens can display more vivid, saturated colours than can be reproduced with CMYK inks on paper. This is why some colours — particularly bright oranges, vivid blues and neon colours — look noticeably different when printed
    • RGB is for screens, CMYK is for print — designing in RGB and converting to CMYK at the end often causes unexpected colour shifts. Always design in CMYK from the start
    • Black works differently — on screen, black is created by turning off all light (0,0,0 RGB). In CMYK, a rich black for large areas is typically created using a mix of all four inks (e.g. C60 M40 Y40 K100), while text is usually set in 100% black (K only) to avoid colour registration issues

    Why You Must Design in CMYK for Print

    Designing in RGB and converting to CMYK at the last minute is one of the most common — and easily avoidable — causes of print colour problems. The conversion process cannot add colour information that doesn't exist in CMYK, so some RGB colours simply cannot be reproduced accurately in print.

    The solution is simple: set your document to CMYK mode from the very beginning of your design process. In Adobe Illustrator, Photoshop or InDesign, set the document colour mode to CMYK before you start designing — not after. This ensures every colour choice you make is achievable in print from the outset.

    Best Practices for CMYK in Print Design

    • Set up in CMYK from the start — in Illustrator: File ? Document Colour Mode ? CMYK. In Photoshop: Image ? Mode ? CMYK. In InDesign: File ? Document Setup ? Intent: Print
    • Check your blacks — use 100% K only for text and thin lines. Use a rich black mix for large dark backgrounds to avoid a washed-out appearance
    • Be aware of colour shifts — if you're working with a brand colour originally defined in RGB or as a Pantone colour, check its CMYK equivalent carefully and adjust if the conversion produces an unsatisfactory result
    • Use Pantone references for brand-critical colours — the Pantone Matching System provides standardised colour references that can be converted to their closest CMYK equivalent for process printing. See our full Colour Guide for Printing
    • Request a proof for colour-critical jobs — a printed proof lets you check colours before committing to a full print run
    • Export as PDF with correct colour settings — when exporting for print, ensure your PDF export settings preserve CMYK values and do not convert to RGB

    Common CMYK Mistakes to Avoid

    • Designing in RGB and converting at the end — always start in CMYK
    • Using neon or very saturated colours — these often fall outside the CMYK gamut and will print noticeably duller than they appear on screen
    • Using RGB black (0,0,0) for large areas — this typically prints as a flat, slightly grey-looking black in CMYK. Use a rich black mix instead
    • Placing RGB images in a CMYK document — images placed in your layout must also be in CMYK. Convert all placed images before finalising your artwork
    • Not proof checking before submitting — always review your artwork carefully. See our proof checking guide for a full pre-submission checklist

    Print with Accurate Colour at Dipol Print

    At Dipol Print, we print business cards, flyers, posters, brochures, banners and much more for businesses across Brighton & Hove and the wider UK. Our team is always happy to advise on colour setup and artwork requirements — just get in touch or visit us at 97 St James's Street, Brighton BN2 1TP.

    Not sure if your colours are set up correctly? Send us your artwork file and we'll check it before you place your order.