CMYK vs RGB: Why Printed Colours Look Different
Design in CMYK for print and RGB for screens. Here is what actually shifts when a file is converted, which colours are most at risk, and how to keep your brand colour consistent across paper, signage and apparel.
The actual difference in one paragraph
RGB is additive. A screen starts black and adds red, green and blue light to build a colour. Add all three at full strength and you get white. Because the screen is emitting light directly at your eye, it can hit colours that genuinely glow.
CMYK is subtractive. Paper starts white and ink is layered on to absorb (subtract) light. Cyan, magenta and yellow together theoretically make black, but in practice they make a muddy brown, which is why a separate black — the K, for “key” — is used. Every colour you see on a printed piece is reflected light that has had part of the spectrum absorbed by ink.
That difference is why the two cannot fully overlap. A screen adding light can be brighter than a sheet of paper reflecting it. No ink is going to out-glow a backlit display.
Which colours actually shift, and by how much
Most colours convert with no visible change. The ones that move are the ones sitting outside what ink can reproduce — what printers call being out of gamut. In practice the repeat offenders are:
- Vivid blues — the single most common complaint. A bright electric blue on screen tends to come back slightly purple in print.
- Bright oranges and reds — often lose a little punch and read slightly deeper.
- Neon and fluorescent anything — cannot be reproduced in standard CMYK at all. Neon green, hot pink and safety orange all convert to a noticeably flatter version.
- Rich greens — emerald and similar saturated greens soften.
Neutrals, skin tones, most photography, blacks, greys and pastels convert without anyone noticing. If your brand palette avoids the four categories above, this whole issue may never affect you.
What to actually do with your files
Design in CMYK from the start if the piece is going to print. In Illustrator or InDesign that is a document colour-mode setting; in Photoshop it is Image → Mode → CMYK Color. Starting in the right mode means you are choosing from colours that can actually be printed, rather than picking something beautiful and discovering later it was never achievable.
If you already designed in RGB, convert and then look at it. The conversion itself is one click. The part people skip is reviewing the result — open the converted file and check specifically the saturated areas. If a colour has gone flat, you can usually hand-adjust it to something closer to your intent than the automatic conversion produced.
Send us the file either way and ask. We check colour mode as part of prepress. If something in your artwork is going to shift noticeably, it is far better to hear it from us before the run than to open the box and be surprised. That check is part of every quote we send.
If your brand colour has to be exact
CMYK gets close to most brand colours but it is a four-ink approximation. When a colour has to be exactly right every single time — a logo that appears across packaging, signage, uniforms and vehicles — the answer is a spot colour, specified by a Pantone reference. A spot colour is a specific ink mixed to that recipe rather than simulated from four process inks.
That matters most on screen printing, where inks are genuinely mixed to a Pantone reference before the run. Full-colour digital methods like DTF apparel printing work in process colour, so they get very close but cannot guarantee an exact Pantone match.
The practical advice: if you have a Pantone code, send it with your artwork. If you do not have one and colour consistency matters to your brand, it is worth establishing one now — it is the reference every future supplier will work from.
Why your monitor is not a reliable preview
Even with a correct CMYK file, your screen is showing you a simulation. Two things work against it:
Your display is probably not calibrated. Brightness, contrast and colour temperature vary enormously between monitors, and most people run their screens far brighter than print will ever appear. A colour that looks right on a bright display can look heavy on paper.
Paper changes the result. The same ink on gloss, matte and uncoated stock produces visibly different colour. Uncoated paper absorbs more ink and reads softer and slightly darker; coated stock holds ink on the surface and looks more saturated. This is also why a colour matched perfectly on a business card can look subtly different on a flyer in the same brand kit — different stock, same ink.
If exact colour genuinely matters for your job, ask about a physical proof before the full run. Looking at the actual ink on the actual stock is the only preview that tells the truth.
Does this apply to printed clothing too?
Yes, with an extra wrinkle: garments are not white paper. A colour printed on a heather grey tee interacts with the fabric underneath it, and on dark garments a white underbase is laid down first so the colours have something to sit on. Both affect the final appearance.
Fabric also has texture and absorbency that paper does not, so the same artwork reads slightly softer on cotton than it does on a coated flyer. This is one of the reasons we send a free mockup before production on every apparel order — so you are approving how the design sits on the actual garment colour, not imagining it.
If you are matching apparel to printed collateral for an event or a uniform program, tell us up front. We will get them as close as the two materials allow and be straight with you about where a compromise is unavoidable.
Frequently asked questions
Should I use CMYK or RGB for printing?
CMYK. Presses print with cyan, magenta, yellow and black ink, so a CMYK file is already in the colour space the press works in. An RGB file will be converted at some point in the process, and if that conversion happens without anyone reviewing it, saturated colours can shift in ways you did not intend.
Why do my printed colours look duller than on my screen?
Because a screen emits light and paper reflects it. RGB can produce colours that are genuinely brighter than ink on paper can achieve, so the most saturated colours have to be approximated when converted to CMYK. Vivid blues, bright oranges, neons and rich greens are the usual casualties. Neutrals, skin tones and most photography convert without a visible change.
How do I convert RGB to CMYK?
In Photoshop it is Image → Mode → CMYK Color; in Illustrator and InDesign it is a document colour-mode setting. The conversion is one click — the important part is reviewing the result afterwards, particularly any saturated areas, and hand-adjusting anything that has gone flat rather than accepting the automatic result.
Can you print neon or fluorescent colours in CMYK?
Not in standard four-colour process. Neon and fluorescent colours sit well outside the CMYK gamut and will convert to a noticeably flatter version. If a fluorescent colour is essential to the design, it needs a specialty ink rather than process colour — tell us before you finalise the artwork and we will talk through the options.
What is a Pantone colour and do I need one?
A Pantone reference specifies an exact ink recipe rather than approximating a colour from four process inks. You need one if your brand colour has to be identical across packaging, signage, uniforms and vehicles. It matters most for screen printing, where inks are genuinely mixed to that recipe. Digital full-colour methods get close but cannot guarantee an exact match.
Will you tell me if my colours are going to shift?
Yes. Checking colour mode and flagging out-of-gamut colours is part of our prepress review, and we would far rather raise it with you before the run than have you open the box and be surprised. Send the file with your quote request and we will look at it.
Not sure if your file is print-ready?
Send it over with your quote request. We check colour mode, resolution and bleed before anything goes to press, and we will tell you what needs fixing rather than printing it wrong.