CMYK vs RGB: why colours look different on screen and on paper

You have designed a great logo. On screen it glows in a vivid blue, but when the printed business cards arrive, the blue suddenly looks greyer and darker. This is not a printing mistake, and it is not always the designer's fault either. The reason is physics: a screen and a sheet of paper create colour in completely different ways. In this article we explain in plain terms what RGB and CMYK are, why the difference appears, and what you can do so the finished product looks the way you intended.

What RGB is — colour made of light

RGB stands for Red, Green and Blue. It is the colour model used by every screen: computer monitors, phones, TVs and projectors. Each pixel consists of three tiny light sources, and by changing their brightness the screen produces the whole spectrum of colours.

RGB is an additive model. Colours are added together, so the more light there is, the lighter the result. All three channels at full power give white, and when they are all switched off, you see black.

RGB can display very bright, saturated colours — neon green, electric blue, vivid orange.
It is the right format for anything that will be viewed on a screen: websites, social media, newsletters and presentations.
Most cameras, phones and design applications work in RGB by default.

What CMYK is — colour made of ink on paper

CMYK stands for Cyan, Magenta, Yellow and Key (black). These are the four process inks used by offset printing and by most digital presses.

CMYK is a subtractive model. Paper does not emit light — it reflects the light around it. Each layer of ink absorbs, or “subtracts”, part of that reflected light, so the more ink you apply, the darker the result. In theory cyan, magenta and yellow combined would make black, but in practice you get a muddy brown, which is why a separate black ink is added.

Ink is printed as a screen of tiny dots that the eye perceives as a smooth tone from a normal viewing distance.
The final colour depends not only on the ink but also on the paper, its whiteness and its surface.
The CMYK colour range is narrower than RGB.

Why colours change — it is all about gamut

Every colour model has its own gamut — the full range of colours it can reproduce. The RGB gamut is considerably wider than the CMYK gamut. That means some of the colours you see on screen simply cannot be reproduced with four inks on paper.

When an RGB file is converted to CMYK — whether you do it yourself or the print software does it automatically — any colours outside the CMYK gamut are replaced with the closest possible shade. Usually that shade is less vivid and slightly duller.

The colours that suffer the most are:

Bright blues and purples — they turn greyish or shift towards violet.
Neon and light greens — they lose their glow and look muted.
Bright oranges and reds — they can become brownish and less punchy.
Turquoise — often ends up as a plainer blue-green.

On the other hand, natural and softer tones — skin tones, earthy colours, pastels — usually change very little in conversion.

How paper and materials affect colour

Even the exact same CMYK file will look different on different materials. That is why in print we talk not only about the colour model but also about what you are printing on.

Coated paper — a smooth surface keeps the ink on top, so colours look brighter and have more contrast. Ideal for brochures, catalogues and business cards.
Uncoated paper — offset or design papers absorb more ink, so tones become softer and slightly darker. Often used for letterheads, notepads and products with a more natural look.
Recycled and tinted paper — the base shade of the paper affects every colour, because CMYK does not print white: the white is the paper itself.
Films, stickers and textiles — each material behaves differently, and the result can differ noticeably from paper.

The printing technology plays a role too. Digital printing and offset use different inks and screening methods, so a perfectly identical colour between them cannot always be guaranteed. If exact colour consistency across different print runs matters for your brand, mention it right at the start of your order.

Colour profiles — what they are and which one to use

To make the RGB-to-CMYK conversion predictable, designers use ICC colour profiles. A profile describes how a particular press reproduces colour on a particular type of paper. The right profile helps your software calculate more accurately how an RGB colour will look once printed.

The most common profiles in Europe are:

ISO Coated v2 (FOGRA39) or the newer PSO Coated v3 (FOGRA51) — for coated paper.
PSO Uncoated v3 (FOGRA52) — for uncoated paper.

If you are not sure which profile to use, the simplest thing is to ask your print house. We will always tell you which profile best matches the paper and printing method you have chosen.

Another important concept is total ink coverage. If all four inks are at 100% in one spot, that adds up to 400%, and paper simply cannot absorb that much ink — it smudges and takes a long time to dry. For coated paper the usual recommendation is to stay below roughly 300%, and even lower for uncoated paper. The right colour profile applies this limit automatically.

Black — one of the most common mistakes

Black seems like the simplest colour, yet it causes a lot of confusion. RGB black (0, 0, 0) converted to CMYK often becomes a mix of all four inks. That is a problem for small text, because even the slightest misregistration makes the letters look blurry.

For text, use black only: C0 M0 Y0 K100. This gives crisp, clean lettering.
For large black areas, use a so-called rich black, for example C60 M40 Y40 K100. It looks deeper and denser than pure K100, which can appear greyish over a large area.
Avoid C100 M100 Y100 K100 — that is 400% ink coverage and leads to smudging and drying problems.

Pantone and spot colours

If your brand colour has to be exactly the same on every business card, brochure and package, CMYK is not always the best option. In those cases printers use Pantone or spot colours — pre-mixed inks with a standardised reference number.

Pantone colours can be brighter than CMYK and include metallic and fluorescent shades.
They keep the colour consistent across print runs and suppliers.
Pantone is typically used in offset printing and larger runs, because each spot colour needs its own printing plate.
In digital printing, Pantone colours are simulated with CMYK, and some can only be matched approximately.

If your brand has a defined Pantone colour, always include it with your order. That way we can advise whether to print with a spot colour or whether a CMYK version will be accurate enough.

How to prepare your file so the colours come out as expected

Here is a practical checklist to help you avoid unpleasant surprises:

Work in CMYK from the start if the design is meant for print. You will see more realistic colours while you work.
If your file is in RGB, convert it to CMYK yourself and review the result before sending it to the printer. That way you will spot colours that change noticeably and can adjust them.
Use the correct colour profile for your paper type.
Turn on soft proofing (Soft Proof or Proof Colors) in your design software — it shows an approximation of the printed result on screen.
Calibrate your monitor if you work with colour regularly. An uncalibrated screen may be too bright or have a bluish cast, and then every print will seem “wrong”.
Check your blacks — K100 for text, rich black for large areas.
Export a print-ready PDF with the correct settings, for example PDF/X-1a or PDF/X-4.

When it is worth ordering a proof

If colour accuracy is critical — for brand packaging, a large catalogue or a product that will be printed in thousands of copies — the best way to remove the risk is a print proof. It is a sample print on the chosen material that you can inspect and approve before the full run goes to press.

A proof shows real colours on real paper, not on a screen.
It helps you decide between several paper options.
It saves time and money if something needs to change.

Look at the proof in daylight or under neutral lighting, because a warm, yellowish lamp also changes how you perceive colour.

Summary

Screens and paper speak different colour languages. RGB is light and can show brighter colours, while CMYK is ink on paper, with a narrower but realistic range for print. A small difference between screen and print is normal, but with the right colour mode, profile, black settings and, when needed, a proof, you can achieve a very accurate result.

If you are not sure whether your file is ready for print, send it to us. The NRJ team will check the colours, recommend the best paper and printing method, and help you avoid surprises.

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