CMYK vs RGB: why menu colours shift in print

The green that looked like a garden on your laptop will look like a pea soup on 350 g board if you send an RGB file and hope. Screens mix light (red, green, blue). Presses and most digital printers mix ink (cyan, magenta, yellow, black). The two gamuts do not match. Bright screen greens, electric blues and the neon of a social post sit outside what CMYK can hold. They do not “print a bit duller”. They change family. If you have ever approved a proof on a phone and hated the carton that arrived, this is why.

What each space is for

RGB is for things that emit light: phones, the 3D preview, a website. sRGB is the usual assumption; Display P3 is wider and even more optimistic. CMYK is for things that reflect light: paper, toner, offset ink. A restaurant menu is a CMYK object even if you designed it in RGB. The conversion will happen somewhere: in your export, at the RIP, or as a desperate guess on the machine. You want it to happen on purpose, with a profile, before you like the colour.

For short European runs, the working profile is still most often Fogra39 / ISO Coated v2 for coated stocks, or a matching uncoated profile if the board is raw. Ask which profile the output expects and convert to it. Do not send “RGB, convert for me” and then complain that the burgundy is brown. Someone did convert it. They did not have your screen.

The colours that fail first

Pure RGB green (0, 255, 0) has no honest CMYK cousin. It becomes a muddy yellow-green. RGB blue (0, 0, 255) becomes a purple or a dull navy. Saturated oranges flatten. Deep screen blacks that are only R0 G0 B0 become a weak 100 K, which looks thin on coated stock next to a photo. If the brand lives on those colours, redesign the brand for print or accept a different object in the hand.

• Build dark boards as a rich black (for example 60C 40M 40Y 100K on coated), not as 100 K alone and not as RGB black.
• Keep body type as a single strong K, or a very dark CMYK mix you have proofed. Registration on small type is unforgiving.
• Photographs: convert with perceptual or relative colorimetric intent and look at the result, especially reds of tomato and meat.
• Logos: ask for a one-colour and a CMYK version. A web SVG in RGB is a sketch, not a print file.

Soft-touch film and uncoated stock both swallow saturation. A colour that just survives on a glossy laser proof will look quieter on 350 g matte. That is not a printer error. That is the paper you chose for fingerprints. Proof on the stock, or at least on a matte close to it, under 2700 K restaurant light, not under the office tube.

A file that survives the RIP

Export a PDF/X (X-1a or X-4, as specified) at 300 dpi for images, with fonts embedded, 3 mm bleed and crop marks. Convert colours to the agreed CMYK profile in the layout, not as an afterthought in a generic “press quality” preset that still leaves RGB images. Spot colours (Pantone) are a different conversation: they cost more on a 50-copy run and they still need a drawdown if the brand is fussy. For most independent rooms, process CMYK is enough if the file is honest.

Never judge colour on a phone. Never judge it on a glossy office laser and then print matte. A contract proof is luxury on a short run; a printed page on the real board, folded, at table 6, is the minimum. If the burgundy shifts, fix the mix before you order 80 copies. Reprints to correct colour are the expensive kind of 10 € per menu.

What to do this week

1. Open the file and see whether the brand colour is an RGB hex from the website. If it is, rebuild it in CMYK and write the four numbers on the brief.
2. Convert a photograph of a tomato or a steak and look at it next to the original. If the red dies, recast the photo or the ground.
3. Export PDF/X with bleed. Ask for output on the stock you will buy, even one sheet.
4. Read the sheet at night in the room. Approve or change. Do not approve from a laptop in daylight.

Colour management is not a personality. It is a habit: work in the space of the object, proof in the light of the room, and stop trusting a glowing rectangle to describe ink.

Design for ink, then look at the screen

The screen is a sketch. The board is the menu. If you fall in love with an RGB green, you have fallen in love with a colour you cannot serve. Mix it in CMYK until you can live with the quieter cousin, then print.

In Menu Atelier the downloadable print bundle is built for press: PDF at 300 dpi with 3 mm bleed and crop marks, plus a PNG per face if you need a preview. The 3D view is still RGB, which is useful for layout and a liar for saturation; trust the CMYK file and a paper proof on 350 g matte before you order a run, which we print ourselves with a soft-touch finish and a scored fold on bifolds.