# CMYK vs RGB

> Source: https://www.infinitelibrary.ai/glossary/cmyk-vs-rgb

Last updated: 2026-09-06
Category: Printing & binding
Also called: Colour space · Process colour

RGB is the additive colour model of screens; CMYK is the four-ink model of printing presses. Vivid RGB colours often dull when converted to CMYK.

## Definition

**RGB** (red, green, blue) is how screens make colour: three lights added together, white when all are on. **CMYK** (cyan, magenta, yellow and *key* — black) is how presses make colour: four inks that each absorb light from white paper, darker the more you add. Every photograph, every cover mock-up on a monitor, is RGB; every printed page is CMYK.

The two do not cover the same range. RGB reaches saturated blues, greens and oranges that no mix of four inks can reproduce, so a vivid RGB cover **converts** to a duller CMYK one — the classic "it looked brighter on screen" complaint. Converting the file yourself (with a proof) shows the shift before the printer's automatic conversion does it silently.

Two CMYK habits matter for books: set body text as **100% K** only, never four-colour "rich" black (which mis-registers into fuzzy edges), and keep total ink coverage under the printer's limit, typically 240–300%.

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