"Are the colors set in PMS, CMYK or RGB?"
When designers talk about PMS, they aren't warning you to leave them alone for a few days. (Well, maybe they are, but not for the same reason.) PMS, CMYK, and RGB are all different ways of defining color - and since color is an important part of what we do as a printer, we want to make sure that when we print your pieces, we have consistent color every time. That's why we ask questions, to help us make sure we're doing everything we can to get the best color quality.
But what does it all mean?
RGB - RGB color is based on light. If you stand reeeeeally close to your computer or tv monitor, you'll see tiny specks of red, green and blue light. Different combinations of light create different color - the absence of light makes black, and 100% of all three lights makes white. RGB is used for on-screen color, but not printing.
CMYK - CMYK color is based on pigment, or ink/toner in the printing environment. Cyan, Magenta, Yellow, and Black (K) in different combinations create a wide range of colors. Like your monitors, if you got a microscope and looked at a color printed piece - like a newspaper or magazine - up close, you'd see tiny little dots of each color layered to make up different colors. Unlike RGB, a complete 100% mix of all four creates a rich black, while the absence of color creates white. Digital printers and 4-color presses work in CMYK.
PMS - PMS stands for the Pantone Matching System, which is the universally recognized authority on color consistency and quality. Color is given a PMS value, and along with it, a global standard. PMS 485 (which happens to be AlphaGraphics Red) will be the same shade of red whether it is printed offset or digitally. Pantone is even used in the fashion industry. In the print world, we use Pantone inks in our offset printers, and to help us maintain consistency between digital and offset pieces.