When you call a printer for a quote, they'll ask you questions like:
"Is it four color process?"
"Spot color?"
"What PMS number do you want?"
(Which is NOT about a bad week, so not joking)
If a printer has a problem with the colors in a file you provided, you might hear statements such as:
"All your images are rgb and need to be converted to cmyk"
"There are four different Pantone blues specified in your two-color job, which one should we print?"
What next?
Maybe this will help.
Everything we produce is done with ink or toner, so we think in ink terms. If you give us images in your beautiful magazine as rgb files, they'll need to be changed to cmyk, so we can run separations to plates, so your layout prints correctly on the press.
Most digital color printers can take a file which is rgb and turn it into cmyk, no problem. That is one main difference between digital printers and a four-color press. The printer processes the file at one time, and puts the colors where they go. The press needs a different plate for each color, and as the sheets move through the press, one color after another is added, until you have the full-color finished products at the end.
Pantone colors are a proprietary system that pre-mixes inks. Many of the colors are not achievable with CMYK. The image below shows the difference between a Pantone ink and the closest version in CMYK.
If you look at this closeup of those two swatches below, you can see the dots of color used to make up the blue on the right. That's the reason the Pantone colors are so much brighter in the lighter shades. Pantone is a great way to cut costs by running only two inks on a job, because you can have the impact of color, but use fewer inks. Those jobs are called Spot Color, vs Process (CMYK) Color.
When you're setting up a file that is to be only two colors, you need to make sure that all the images, text, and graphics are defined as either one ink or the other.
For example: You have decided to print a lovely flyer in Pantone Red 032 and 136. While this might not be my first choice for easily readable, it perfectly suits your Improvisational Accounting Troupe's quarterly dance party.
All of your fonts must be in one of these colors and all of your graphics must be in one (or both) of these colors. Setup programs like InDesign, Illustrator, and Quark will allow you to choose these spot color swatches. Photoshop doesn't save spot colors, so your images will have cmyk mixes, unless you save them as black only images, and tell us the black should be the red.
There are several ins and outs with spot colors, channels, monotones and duo tones when working with Photoshop files. That's an entirely different topic. One for another day.
Do you have any questions? I'm happy to answer them! Post in the comments section below and I'll answer as soon as I can.
Happy Colorful Planning!