“The file is RGB, it needs to be CMYK.”
Screens make colour from red, green and blue light (RGB); printing presses make it from cyan, magenta, yellow and black ink (CMYK). The printer wants the file in CMYK so the colours you approve are the colours that print. Converting can make very bright blues, greens and oranges look duller, because ink can’t reach every colour a screen can, so it’s best done by you, on screen, before the press does it for you.
Updated November 3, 2026 · by Azaan Ali, print designerWhy printers ask for this
A printing press has four inks. Every colour in an RGB file has to be translated into those four before it can print. If you hand over RGB, the printer’s software does the translation, and you don’t see the result until the job is printed.
Some RGB colours have no exact CMYK match: electric blue, neon green, bright orange. They shift towards the nearest colour ink can make. Converting yourself means you see that shift first and can adjust it, instead of discovering it in a box of 500 flyers.
How to convert a print file from RGB to CMYK
- Ask your printer which colour profile they use. In North America it’s usually GRACoL or US Web Coated (SWOP); in Europe, FOGRA39.
- Illustrator: File → Document Color Mode → CMYK Color, then check every colour swatch. Photoshop: Edit → Convert to Profile, and pick the printer’s profile.
- Look at the colours that changed most (bright blues, greens, oranges) and adjust them by eye until they’re close enough.
- Make large black areas a rich black (for example C60 M40 Y40 K100), but keep small black text 100% K only.
- Canva: Download → PDF Print and choose CMYK (Canva Pro only).
- Export a PDF/X-1a or PDF/X-4, which keeps everything in print colour.
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- Convert every image, vector and colour to your printer’s CMYK profile
- Hand-adjust brand colours that shift, so they stay as close to your screen as ink allows
- Set rich black for large areas and pure black for text
- Match Pantone (spot) colours if your printer is printing them separately
Questions
- Why does my file look duller after converting to CMYK?
- Ink can’t reproduce every colour a screen can. Very saturated colours move to the nearest printable colour. A designer can pick the best printable match by eye, which is usually much closer than an automatic conversion.
- Can I just send RGB and let the printer convert it?
- Many printers will, but the conversion is automatic and you won’t see the result before it prints. Brand colours are where it matters most.
- What about Pantone colours?
- If your printer is running a Pantone (spot) ink, keep that colour as a named spot colour rather than converting it. We set both up correctly.
Terms on this page: CMYK, RGB, Pantone (spot colour), Rich black.
Other things printers say
More on this kind of work: Print file fixing.
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