RGB vs CMYK: Which Colour Mode Should You Use for Printing?

A design looks vibrant on screen, then the print arrives looking flat and darker. The usual reasons are the difference between RGB and CMYK colour, and a screen that is brighter than paper. Here is what is going on and what to do about it.

RGB and CMYK in one minute

• RGB (red, green, blue) is how screens make colour: by adding light. More light means brighter colours, and all three at full strength make white.
• CMYK (cyan, magenta, yellow, black) is how printers make colour: by laying ink on paper, which absorbs light. More ink means darker colours.

Because light can make colours that ink can’t, some RGB colours simply can’t be printed. The range of colours a device can show is called its gamut, and a screen’s gamut is larger than a typical printer’s in the bright, saturated colours.

Colours that change most

• Neon and electric greens
• Bright, saturated blues and purples
• Vivid oranges and hot pinks

When printed, these are converted to the closest colour the ink can make, which looks duller. Skin tones, earthy colours and pastels usually print close to how they look on screen.

Which should you send?

It depends on who is printing:

Services that want RGB convert your file using profiles tuned to their own printers and paper. Converting to CMYK yourself first can make the result worse, not better. If a printer wants CMYK, they will usually tell you which profile to use (for example FOGRA39 in Europe or GRACoL in the US). When in doubt, ask.

Use sRGB for RGB files

RGB files can carry different colour profiles. sRGB is the standard that almost every print service expects. Files in wider profiles such as Adobe RGB or Display P3 can print with shifted or dull colours if the service ignores the profile. Most editing apps let you convert to sRGB on export.

Preview print colours on screen

Photoshop, Affinity Photo and other editors offer soft proofing, which simulates how a file will look when printed with a given profile. In Photoshop, use View → Proof Setup and turn on Gamut Warning to highlight colours that won’t print as they appear. Adjusting those areas yourself gives you control over how they look, instead of leaving it to the printer.

Why prints look darker than the screen

Screens are lit from behind, and most are set far brighter than a printed page under normal room light. If your prints always come out darker than expected, turn your screen brightness down while editing, or calibrate your monitor. Ordering a small test print is the most reliable check of all.

A note on black

In CMYK, black made from black ink alone can look slightly grey in large areas. Commercial printers often recommend a “rich black” that mixes in some cyan, magenta and yellow for large dark backgrounds, while keeping small text in pure black ink so it stays sharp. Ask your printer for their recommended mix.

In short

• Screens use RGB light; printers use CMYK ink, which can’t reproduce the brightest colours.
• For photo labs, print-on-demand and home printing, send sRGB files.
• For commercial printers, follow their CMYK instructions.
• Soft-proof bright designs and order a test print before printing large runs.

Colour is only half the story: an image also needs enough pixels. Check your image’s resolution before you print.