A screen makes colour by emitting light — red, green and blue, added together, black when nothing is on. A press makes colour by absorbing it — cyan, magenta, yellow and black ink on white paper, white when nothing is on. These are opposite processes, and they cannot reach all the same colours.
Which colours are worst affected
The RGB gamut is larger than CMYK in specific regions, so those are where artwork changes most visibly:
- Bright saturated greens — the most common casualty. They come out noticeably duller.
- Vivid blues, especially electric and royal blues, which tend to shift toward purple.
- Intense oranges and some reds, which lose their glow.
- Anything neon. Neon is light, and ink is not light.
Muted colours, skin tones, greys and most photography convert with very little visible change. If your artwork is photographic — a flyer carrying product shots, say — you will usually not notice.
Convert before you export, not after
If you send an RGB file it gets converted anyway — just not by you. Converting it yourself means you see the shift on your own screen while you can still do something about it, rather than discovering it on the proof.
In Illustrator, InDesign or Photoshop, set the document colour mode to CMYK and look at what moves. If a brand colour drops noticeably, pick the closest CMYK value you are happy with deliberately rather than accepting whatever the conversion produces.
Rich black, and the mistake underneath it
Black text should be 100% K and nothing else. Large black areas can look weak in single-ink black, so a rich black — extra cyan, magenta and yellow underneath — gives more depth.
The mistake is using rich black for body text. Four inks have to register perfectly on top of one another, and at small sizes any tiny movement shows as coloured fringing on the letterforms. Keep type at 100% K.
What our file check does
Every uploaded file is inspected for colour space along with trim, bleed, fonts and image resolution, and you get an on-screen proof before you pay. A warning is advice, not a block — you can acknowledge one and we will print it, and it gets flagged internally for a second look.
What the proof cannot do is show you the exact printed colour on your screen, because your screen is still RGB. If an exact colour match genuinely matters, tell us before you order.
See our file requirements for the full specification.