RGB vs CMYK: the difference

RGB is an additive model that creates color by adding the primary colors of light (red, green, blue). It is used on screens like monitors and phones; adding all of them yields white.

CMYK is a subtractive model that mixes inks (cyan, magenta, yellow, black) to subtract light, and is used for print; adding all of them approaches black.

The two models cover different ranges of color (gamut), so a color that looks vivid on screen can appear duller in print. If your goal is printing, it is best to check CMYK values from the start.