Let’s talk about the three systems of color most designers deal with, RGB, CMYK and spot.
RGB colors are used on screen. It stands for the Red, Green and Blue colors of light that create all the different hues that you see on your monitor. Each of these RGB values can go from zero, which means a color isn’t showing up at all, all the way to 255, which means that the color is at full strength. RGB colors are light based, and they’re for on-screen use.
CMYK colors on the other hand, these are for print media. Especially for a kind of printing called process color printing. CMYK stands for Cyan, and that’s a kind of blue, and Magenta, Yellow and Black. With these four colors , you can come up with any colors that you see in print media. And this happens when various percentages of some or all of these transparent inks are either printed alone, or on top of each other. And they can go from solid or 100% all the way down to 0%. Lighter shades of CMYK colors are made by printing as half-tone percentages, or screen tints. And these are different densities of tiny dots that are usually too small to be seen without magnification.
A spot color is a pre-mixed color of ink. If you want to just print your business cards using say, purple, you can print them using a single-color printing press loaded with just the purple spot color. This, as opposed to printing it using a blend of all four colors needed for process-color printing. Designers can select spot colors from the swatch menus of programs like Illustrator, Photoshop, and InDesign or from printed catalogs and swatch books offered by companies like Pantone. Spot colors are far more dependable for accuracy than CMYK colors.
There are connections between RGB, CMYK and spot colors. For instance, after you choose a Pantone spot color, programs like Photoshop and Illustrator can convert that spot color into a four part CMYK formula. These programs, they can also do their best to translate both spot and CMYK colors to RGB formulas as well. And that way they’ll show up pretty much the way they’re supposed to on your monitor.