"Why does my print come out a different colour? My inkjet at home never does this." It is one of the most common questions designers and clients ask a commercial printer — and the answer is that professional printing is nothing like desktop printing. A finished colour piece runs through a multi-step production process with real technical limits and fixed environmental conditions, and every one of them can nudge the final colour. Graphic designers in particular should understand where these shifts come from, because knowing what is controllable — and what isn't — heads off a lot of arguments over things no one can actually fix.

Print never matches your screen

This one is an old story by now, but it still catches people out. Every monitor renders colour differently depending on the brand, the model and its individual colour settings, so the same file looks different from screen to screen. More fundamentally, a display builds its image from RGB light, while a printed piece is mixed from four CMYK inks. The two work on completely different principles, which is why the colour on screen and the colour off the press can diverge sharply. Never colour-check your job against what you see on a monitor.

The pressroom shifts colour too

Environmental factors add their own variation. Printing time, ink density, temperature, position on the imposed sheet, the characteristics of the paper — these are largely outside human control, and each one can move the printed colour a little.

Gang printing and the ±10% rule

Gang printing combines many separate files onto a single plate, so the press cannot tune or adjust colour for any one layout on its own. If your job sits next to a heavy-ink area, its colour gets pulled in that direction. Say the piece printed beside yours skews red — your colour can shift red by plus or minus 10%. For this reason a ±10% colour tolerance on gang-printed work is normal and expected, and jobs cannot be returned over a difference within that range. Even a reprint from the exact same file will vary, because the imposition position changes every time.

Colour values to check in your file

  • Keep your lightest tint at or above 8%. Anything lighter may simply fail to print.
  • Avoid four-colour (rich) black and four-colour grey. Blacks and greys built from all four process colours are prone to severe colour shifts.
  • Watch total ink coverage. Fills above 200% total ink don't dry easily, which invites set-off and ghosting on the back of the sheet.
  • Convert your images to CMYK. Photos left in RGB will not reproduce as designed.
  • Be careful with sensitive colours. Colours overprinted from two or more inks — purple, brown, orange and the like — turn visibly wrong the moment any single CMYK channel drifts.
  • Avoid spot colours. If your artwork came from a stock library or an outside file, it can carry a hidden spot-colour profile you never noticed, which can throw the whole job off — a full, across-the-board colour shift. Check for this carefully.

Paper changes colour too

Every stock has its own base tone and character. The better you know how a paper behaves, the more confidently you can choose colours for it — which is why we try to introduce the traits of each stock we offer. Because the paper carries its own underlying colour and because every stock absorbs ink differently, the printed ink shifts with the paper. Even a proof can't calibrate this away perfectly; it can only reduce the difference.

Client and printer both wish the colour error could be zero. But real production is bound by too many conditions to eliminate it completely — the most anyone can do is manage it, keeping the variation within a reasonable, agreed colour standard.