Pantone Spot Colors PMS (More expensive, Less common due to cost or need) No, not the lovely monthly "glow" us females get to enjoy. PMS, a.k.a Spot Colors, is a color "language" that produces what most would consider an "exact" color. Basically, it eliminates any variance in color of ink when printed, no matter who, when, or where it is printed in the world. PMS stands for Pantone Matching System. It's a system that assigns a specific sequence of numbers to specific colors. Each number relates to the amount of one of the basic colors (inks) used to create that specific color and shade. It allwos printer's to assure the exact color to print (by entering the PMS color in the system) versus dealing with a limited color pallette of CMYK (Cyan, Magenta, Yellow, Black). Printing in PMS can't be done on a regular printer you have at home, or even a fancier printer you may have in the office. They are special, very large, printers where the printing press technician literally has cans of ink of all different colors to fill the print press with, according to the PMS color code(s) included in the job.
CMYK - (Less expensive, Most common printing method) CMYK or "Digial Printing" is used ff you do not have a need for specific colors, then anything sent to a printer should be sent to a printer with CMYK colors. You may also know of "RGB". That color "language" is used for anythign you view on a digital screen. It is essentially, one less color than CMYK to work with. If you were to print using RGB, your images will undoubtedly not match your intended color. Printing with RGB will lead to a darker or muted/dull output of ink.
How do you know which INK you need to print with? If you are at all worried that color's need to match exactly, Pantone colors or "PMS" inks are the best option to use. All experienced designers are able to work with PMS colors and know how to set-up files for print with them. So, a limited amount of inks (colors) or specific colors for a brand, this is your option. It is often the pricier option for print, but you will save the hastle and cost of re-printing only to hope that the new print comes out better.
So what really is the difference? The best way to explain the difference between using PMS colors and CMYK is you visualize a painter with a pallete of paints. The CMYK painter only has 4 colors to work with on his pallete. The PMS painter has endless shades and colors on his pallete. Illustrator: Go to “File” > “Document Color Mode” and check CMYK.