Every graphic designer has had this conversation with a client. “The red on the website is perfect. Can you make the printed poster exactly the same red?” And the honest answer is: no, not exactly, because the physics of emitting light and the physics of absorbing light are not the same thing.
This disconnect is older than the web. It goes back to the first time a newspaper tried to reproduce a painting, and every technology since, CRT monitors, inkjet printers, LED screens, pigment inks, e-paper, has inherited a version of the same problem. Here is what is happening, why the mismatch is unavoidable, and how to work with it.
Two opposite models
A screen makes colour by adding light. Each pixel has three tiny sources, red, green, blue. Each starts at zero (off). Turn them up and the pixel emits more light. Turn all three up to maximum and you get white.
A printed page makes colour by subtracting light. The paper starts white, it reflects all visible wavelengths. Ink placed on the paper absorbs certain wavelengths. The colour you see is whatever light bounces off after the absorption. Put enough ink down and you absorb almost everything, producing black.
This is the short version. Everything else follows from it.
- Screens are additive: start with black, add light.
- Print is subtractive: start with white, subtract light.
The two models use different primaries because the physics demand it. Additive uses red, green, blue, the three wavelengths that can most efficiently add up to the full perceivable spectrum. Subtractive uses cyan, magenta, yellow, the three pigment colours that most efficiently subtract each of those three wavelengths. CMY is the subtractive mirror image of RGB.
Why K is in CMYK
Pure CMY mixed at 100% should, in theory, absorb all light and produce black. In practice, real pigment inks are never pure. Cyan ink still reflects a little red light. Magenta still reflects a little green. Yellow still reflects a little blue. Mix all three at full strength and you get a muddy dark brown, not a clean black.
Printers solved this by adding a separate black ink, Key, abbreviated K (not B, because B was already used for blue). Key serves three purposes. It produces true black where needed. It saves money, because black ink is cheaper than three coloured inks piled on top of each other. And it sharpens text, because CMY text would have to register three plates perfectly to look clean.
So CMYK = Cyan, Magenta, Yellow, Key (black). Four inks, four plates, one set of tradeoffs.
Gamut, the range each medium can reach
Every colour-reproduction medium can only reach a subset of all perceivable colours. That subset is called its gamut.
- Human vision has the biggest gamut. A person with normal colour vision can distinguish somewhere between 1 million and 10 million distinct colours.
- A modern laptop screen covers roughly 100% of sRGB, which is about 35% of the visible gamut. A premium display covers Display P3 or Adobe RGB, bumping the total closer to 45%.
- A commercial CMYK printer using standard process inks covers maybe 40% of the visible gamut, but a different 40%. There are colours a printer can produce that a screen cannot, and colours a screen can show that a printer cannot approximate.
The two gamuts overlap substantially but do not match. Specifically:
- Bright, saturated greens and blues are easier to produce on a screen. Pure
#00FF00(sRGB green) does not exist in CMYK. A printer trying to reproduce it will shift toward the nearest in-gamut colour, typically a less vivid, slightly yellower green. - Deep oranges and rich browns can be more accurate in CMYK than on sRGB screens. The CMYK gamut extends into regions of the orange/red range that sRGB truncates.
- True neutral greys are easier to print than to display, ironically, because a printer can mix precise amounts of CMY to cancel any warm-or-cool tint, while a screen’s white point is usually slightly blue.
Every mismatch between “how it looked on my monitor” and “how it came out of the printer” has one of these gamut boundaries at its root.
Soft-proofing, seeing print on screen, in advance
Professional designers do not guess. They soft-proof. Soft-proofing is a display mode that simulates how an image will look when printed in a specific ink-paper combination.
The designer selects a CMYK profile (for example, US SWOP Coated v2, which is a standard American commercial printing specification). The design software, InDesign, Photoshop, Illustrator, shifts every on-screen colour toward its nearest in-gamut CMYK equivalent, and dims the whole image slightly to simulate the reflective nature of paper rather than the emissive nature of a screen.
The result is an on-screen preview that is a closer approximation of the print output. It is still not perfect, no screen can accurately preview ink on paper, but it is much closer than working in unconstrained RGB and hoping for the best.
On colour.love, the adopted colours are displayed in sRGB. If you print an adopted colour on a business card or a poster, expect some shift. Saturated colours will shift the most; muted mid-tone colours will shift the least.
The Pantone shortcut
For brands that cannot tolerate gamut shift, think Coca-Cola red, UPS brown, John Deere green, the industry uses Pantone Matching System colours. PMS is a physical library of pre-mixed inks with fixed recipes. Instead of building a brand red from four CMYK plates (which will shift slightly between print runs), the printer uses one ink mixed to a specific Pantone number. It is called a spot colour.
Pantone inks can reach colours outside the CMYK gamut. That is their main appeal. Metallic golds, fluorescent oranges, a specific corporate red, all of these are Pantone spot colours that CMYK process printing cannot reproduce.
On a screen, Pantone codes are approximated. Adobe software ships with a library of Pantone-to-sRGB conversions that are as close as the gamut allows. These approximations are often visibly different from the ink sample. The ink sample is authoritative. The screen preview is advisory.
Pantone, the company, got into a notorious fight with Adobe in 2022 over licensing fees for this library, and briefly pulled support from Creative Cloud. The fight is a good reminder that “the Pantone colour” is a commercial standard owned by a specific corporation, not a neutral public reference. Every industry has one of these. Colour has several.
A rule of thumb
If you are designing for screen only, web, mobile, broadcast, author in sRGB or Display P3, use hex or OKLCH notation, and do not worry about print. The gamut is consistent across modern devices.
If you are designing for print only, books, packaging, newspapers, author in CMYK from the start. Pick a paper stock early. Use Pantone for critical brand colours. Soft-proof throughout.
If you are designing for both, which is most brands, establish the brand colour as a Pantone spec first, derive the CMYK approximation for print, and derive the sRGB hex for screen. Document all three values in the brand guidelines. When they do not match perfectly (they will not), document that too.
The goal is not to pretend the two mediums can show the same colour. The goal is to decide, in advance, how much drift is acceptable at each touchpoint, and to know when you have exceeded the budget.
Which brings us to a question
When you adopt a colour on Colour Love, you are naming and claiming an sRGB code. That code is stable and portable. A printer, with your permission, can attempt to reproduce it in CMYK or in a Pantone spot ink. The result will be close to the screen version, not identical. That is not a failure of our platform. It is the geometry of additive and subtractive colour. The web is a light source. Paper is not. Both are beautiful. Neither can quite be the other.