01In plain English
Screens mix red, green and blue light (RGB). Printers mix cyan, magenta, yellow and black ink (CMYK). Some bright screen colors cannot be printed, so print work is prepared in CMYK to see the real result.
02How it works
A screen makes color by shining red, green and blue light, and mixing all three makes white. A printing press works the other way, laying cyan, magenta, yellow and black ink on white paper, and the more ink it uses, the darker the result. Because ink cannot reproduce some of the brightest screen colors, a vivid electric blue on your monitor can print as a duller shade. A CMYK editor shows you the printable version while you work, so you can adjust before the file reaches the printer. The printer then makes plates or sets its machine from those four values. It is like checking how a photo will look on newsprint before you commit to the print run.
03Why it matters when you are choosing
If you design for print, an editor without CMYK can hand the printer colors that come out dull or shifted. For screen-only work it does not matter.
04What to check
Check whether the editor can work in CMYK and export print-ready PDFs, or only converts at export.
05Where you will meet it
06Common questions
Should I design in CMYK or RGB?
Use CMYK for work that will be printed, so you see colors close to the printed result. Use RGB for anything shown on screens, such as websites and social posts. If you are unsure, ask your printer, who can tell you which color mode and profile they want.
Why do my printed colors look duller than my screen?
Screens glow and can show brighter, more saturated colors than ink on paper can. Colors outside the printable range get pulled toward the nearest match. Working in CMYK, or using a soft proof, shows this before printing so you can adjust.
Can I convert RGB to CMYK later?
Yes, but the colors will shift, and you cannot always get the shift back. The cleanest way is to start in CMYK when you know the job is for print, or at least to convert early and fix any colors that changed before you finish the design.