Short answer
RGB describes color through red, green, and blue light; CMYK describes it through cyan, magenta, yellow, and black ink. Creative workflows generally associate RGB with screens and CMYK with print, but a printer may accept RGB data and convert it. Conversion cannot preserve every bright screen color in ink. 1 2
On this page
At a glance
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| Attribute | RGB | CMYK |
|---|---|---|
| Components | Red, green, blue | Cyan, magenta, yellow, black |
| Reproduction context | Emitted light | Printed ink |
| Values shown in the sources | 0–255 per component | 0–100% per component |
| Main conversion concern | Some colors exceed printable range | Cannot reproduce every RGB color |
These are model and workflow distinctions, not interchangeable numerical scales. 2
What each thing is
A color model is an abstract numerical description of color. In RGB, increasing emitted light moves toward white; zero light gives black. In the guide’s CMYK explanation, no ink leaves white, while maximum black ink produces black. The two models describe different ways of producing an appearance. 2
Key differences
The important reproduction limit is gamut: the range of colors available. Both models have limits, but the sources describe RGB as having a wider range than CMYK. Especially bright, vibrant screen colors may have no printable CMYK counterpart, so converting their numbers does not mean reproducing their appearance exactly. 1 2
How to tell them apart
Inspect the document’s color mode or component labels rather than its intended destination alone. Red/green/blue values indicate RGB; cyan/magenta/yellow/black percentages indicate CMYK. In web design, six-digit hexadecimal notation commonly expresses RGB. The limit: an RGB document can still be destined for printing, with conversion handled downstream. 1 2
Where they overlap
Both models can participate in one publishing workflow. UCLA’s guide describes using a printer-and-paper profile to translate RGB data for CMYK ink output. Soft-proofing previews that translation approximately; it connects screen editing with print reproduction rather than making the two models equivalent. 2
Edge cases
A printer’s input convention need not match its inks. The DMA printers discussed in the guide can be treated as RGB devices even though they print with CMYK inks; third-party RIP software would instead favor CMYK data. Thus, “print means CMYK” is useful shorthand, not a universal file-submission rule. 2
Why the distinction exists
The distinction separates descriptions of light from descriptions of ink. Screen-oriented design and print production therefore have different reproduction constraints. Printer-and-paper profiles matter because the conversion is tied to a particular output setup, rather than being a context-free replacement of three values with four. 1 2
Common misconceptions
Changing notation is not the same as changing models: hexadecimal RGB and decimal RGB are two representations of RGB values. Nor does finding a CMYK equivalent establish an exact ink match; BYU describes CMYK equivalents of formulated Pantone inks as producing similar tones. 1
Examples
Hypothetical case 1: A vivid website graphic is reused in a printed flyer. Its bright RGB colors may shift because some fall outside CMYK’s reproducible range. Hypothetical case 2: An RGB document is sent to one of the DMA printers described by UCLA. It remains RGB input even though the output uses CMYK inks. 2