CMYK vs. RGB
CMYK is an acronym for Cyan, Magenta, Yellow and Key (Black)—the colours of the inks that are used in four-color process print.
RGB is an acronym for Red, Green and Blue—the colours of light that are displayed on a digital screen.
If colour conversion is not done correctly, the resulting print may miss colours that were intended to be used, or even include ones you never asked for. It may lack vibrancy or clarity that can reflect poorly on your brand.
CMYK involves a process where each ink colour overlaps to create a subtractive colour spectrum. So the more ink, the less light is reflected back from the paper and the more colour you overlap, the darker the resulting hues.
RGB is an additive colour spectrum. In this colour space, the more overlapping colour you add, the lighter the resulting image. This is opposite of the CMYK process. The RGB color spectrum is larger than that of CMYK, so what you see on your computer monitor may not be compatible with your printer. Use CMYK colour builds to avoid potential RGB conversion issues.
If you’re working on Adobe Illustrator, you can check how the image will look when converted to CMYK by choosing View > Proof Colors. Here, you will be able to see how saturated colours look much duller when converted from RGB to CMYK. Monitor calibration softwares can also help your screen more accurately approximate the printed result. In all, just know that RGB = Web Design, and CMYK = Print Design.