What’s the Difference Between CMYK and RGB?

One of our clients once asked me to explain what CMYK meant and what the difference was between it and RGB. Here’s why it’s important.
We were discussing a requirement from one of their vendors which called for a digital image file to be supplied as, or converted to, CMYK. If this conversion is not done correctly, the resulting image might contain muddy colors and lack vibrancy which could reflect poorly on your brand.
CMYK is an acronym for Cyan, Magenta, Yellow and Key (Black)—the colors of the inks that are used in common four-color process printing. RGB is an acronym for Red, Green and Blue—the colors of light that are utilized in a digital display screen.
CMYK is a widely used term in the graphic design business and is also referred to as “full-color.” This printing method utilizes a process where each ink color is printed with a particular pattern, each overlapping to create a subtractive color spectrum. In a subtractive color spectrum, the more color you overlap, the darker the resulting color. Our eyes interpret this printed color spectrum as images and words on paper or printed surfaces.
What you see on your computer monitor may not be possible with four-color process printing.

RGB is an additive color spectrum. Basically any image displayed on a monitor or digital display screen will be produced in RGB. In this color space, the more overlapping color you add, the lighter the resulting image. Almost every digital camera saves its images in the RGB color spectrum for this reason.

The RGB color spectrum is larger than that of CMYK
CMYK is for printing. RGB is for digital screens. But the thing to remember is that the RGB color spectrum is larger than that of CMYK, so what you see on your computer monitor may not be possible with four-color process printing. When we are preparing artwork for our clients, careful attention is given when converting artwork from RGB to CMYK. In the example above, you can see how RGB images that have very bright colors could see unintended color shift when converting to CMYK.