PMS color is an actual ink that is purchased in the desired hue – not mixed from the traditional cyan, magenta, yellow, or black inks.
Think of it it terms of nail polish or car paint. You don’t buy a blue color paint and try to mix it with a yellow paint in order to touch
up your green car. instead, you buy the manufacturer paint for your exact vehicle and color, so when you do the touch up it
matches you car perfectly. Likewise, when you print a PMS color it should match perfectly from the first print to the last, even if
you print at different printers, and even if you print your pieces at different times.