So far we have discussed the CMYK Color Space and the RGB Color Space, now we need to go back a few years and talk about Spot Color Printing.
The offset printing process is sort of like a box of Crayons. When you setup your press you have an ink fountain that you fill with your ink, think of this as choosing you the color of your crayon.
Most presses years ago were only single or two color presses which meant that you could only “color” with either one or two colors at a time (in essence the number of ink towers on the press) Until recent years that was the most common type of however now most presses today are setup with at least four towers to support the fours colors of Cyan Magenta Yellow black (CMYK) process printing.
Printing presses that support less than 4 colors at one time are “typically” used only for Spot Color printing and usually use the Pantone Matching System (PMS) to communicate the correct color from the designer to the pressman. The PMS system allows everyone to have a common reference point to discuss colors.(I am sure you have seen the little fanfold books what looks like an infinite number of choices) The challenge is that the PMS system was developed long before it was common to produce jobs using the CMYK process and because the colors that are used to “mix” PMS color are not CMYK it causes some colors to change slightly while others may look totally different.
To help with this crossover of colors from PMS color to CMYK color most printers have a PMS Bridge book that can show you what you can expect the color to look like.
Here are a few side by side examples…