How we see color: RGB/CMYK.

Like PPI and DPI, RGB and CMYK refer to digital versus physical media. RGB refers to Red, Green, Blue, which are the colors of the light spectrum that are needed to craft the full rainbow. CMYK stands for Cyan (a rich, turquoise-y blue), Magenta (a well-loved hot pink), Yellow (like pure sunshine) and K (black). Files are required in RGB because that is the format in which they are manipulated on the computer screen. All files stay in RGB until they are converted to CMYK by the printer drivers. Digital printing as we know it follows this conversion process. If you send a CMYK file to print through the printer driver, some colors and especially the black point will be altered and won't match what you originally saw on your screen.

TIP: When making your final save, set your monitor to 50% brightness to mimic the difference of reflected light off a print versus the backlit light from a monitor.