You might find out that a particular shade of blue that looked great on the screen has lost its saturation on paper or that a brilliant green on screen turns to a more muted version on paper. That doesn’t necessarily mean that something went wrong with the printer. The way the screen generates color is different from the way the printer generates color. A design that looks vibrant in RGB may change to a more muted color palette when converting to CMYK before it’s printed. It is important to learn how to expect color shifts during the print process.
The RGB color model uses the red, green, and blue colors and combines them on a screen. This allows RGB to be more vibrant and have high saturation levels. CMYK is based on cyan, magenta, yellow, and black. The printer uses these inks in combination on paper. Paper and inks reflect rather than produce color and the color that is produced on the printer depends on the paper that was used. Because the CMYK color gamut is smaller, vibrant blues, bright greens, vivid oranges, and neons may not print with as much saturation as they looked on the monitor.
This is not always so obvious because you can open an RGB file in Illustrator and you won’t immediately know that something is wrong. You might finish the document, create the final PDF, and then not see a proof until you receive the printer’s proof and suddenly notice a color shift. Another area that is confusing to people is that just converting the document to CMYK won’t necessarily produce the correct color in all cases. The printer may be using a different CMYK profile, the total ink coverage might vary, the paper stock may be different, or you may be printing on an offset printer or in a digital press. Because different types of stock absorb different amounts of ink, the same color values may produce a different look depending on if you’re printing on a coated or uncoated stock and whether you’ll be getting the sharper look on the coated stock or the slightly duller look on the uncoated stock.
For all these reasons, you should review color prior to exporting your final PDF for a print job. Take a look at the document color mode, check the imported photos and any raster graphics, and identify colors that will be beyond the printable gamut. Check the colors in your logos and vector graphics, especially if the specific brand color is a crucial element in the design. If your printer recommends a CMYK profile, be sure to check that. When using a brand color, find out if it might be best to use a spot color rather than a CMYK equivalent.
To learn how your colors will change before you go to the printer, create a test layout with some different color samples: a bright blue, a bright green, bright oranges, a dark neutral color, your photo, and an example of a gradient. Duplicate that page or spread. Then convert the copies to a CMYK profile and see how they change. Try to compare your RGB and CMYK versions at the same zoom level. Now export your final PDF with these tests in the file and then print it on your office printer to check the color and see what you got right. It won’t necessarily reflect exactly how the printer will print the job but you can see where the colors have changed. You may see that you’ve gotten some color shifts or saturation losses or perhaps you didn’t realize that your colors are becoming so dark they are going together in places and you’ll know which colors to change, or you’ll find out your gradient may have banding. Make sure you keep the sample document and the original color values so you can see how much the CMYK version changed compared to the original.
You may be tempted to try to get the color right before you get the final PDF, but it’s better to make a decision if you want the colors in the CMYK version to match the vibrant RGB version or if they just need to be acceptable enough on their own. In some cases, the color may still be good, even if it’s less saturated. What matters most is that there’s sufficient contrast for reading the message and that the hierarchy of the information remains correct. Look at your final proof under typical lighting conditions before you go to print and decide if the color is what you want for the piece rather than trying to determine if it matches the way it looks on the monitor.