The PANTONE Matching System (PMS) is the dominant spot color printing system in the United States. Printers use a special mix of ink to achieve the color needed. Each spot color in the PANTONE system is assigned a name or a number. There are over one thousand PANTONE spot colors available.
Are PANTONE 624 U, PANTONE 624 C, PANTONE 624 M the same color? Yes and No. While PANTONE 624 is the same ink formula (a shade of green), the letters that follow it represent the apparent color of that ink mix when printed on different types of paper.
The letter suffixes of U, C, and M tell you how that particular color will appear on uncoated, coated, and matte finish papers, respectively. The coating and finish of the paper affects the apparent color of the printed ink even though each lettered version uses the same formula.
In Illustrator, 624 U, 624 C, and 624 M look exactly the same and have the same CMYK percentages applied to them. The only way to truly tell the difference between these colors is to look at an actual PANTONE swatch book.
PANTONE swatch books (printed samples of ink) come in uncoated, coated, and matte finishes. You can use these swatch books or color guides to see what the actual spot color looks like on the different finished papers.
The PANTONE swatch libraries that reside in Illustrator CS contain CMYK representations of what the PANTONE ink will look like when printed using a spot color plate. The CMYK values were given to Adobe by PANTONE and are stored within the PANTONE swatch. When these swatches are converted to CMYK colors, or printed as process colors, the CMYK representations inside the PANTONE swatch are used. For example, if you take an object with PANTONE 2905 C applied to it (which has a CMYK representation of C=41/M=2/Y=0/K=0), and run the Filter > Colors > Convert to CMYK command on the object, the object will have the values of C=41/M=2/Y=0/K=0.
The PANTONE swatch libraries that reside in Illustrator CS2 and later have both LAB and CMYK representations of what the PANTONE ink will look like when printed using a spot color plate. Both the LAB and CMYK values were given to Adobe by PANTONE and are stored within the PANTONE swatch. Illustrator CS2 and later gives you the ability to choose either the LAB color definitions or the CMYK color definitions when using PANTONE libraries. You can choose which color definition you want to use by selecting Spot Colors from the Swatches panel menu and then choosing the desired color definition.
The CMYK color definitions are the same as those in Illustrator CS and convert to a process color within the application or print from the application as process colors the same way they do in Illustrator CS.
The LAB color definitions in Illustrator CS2 and later mirror the LAB color definitions in Photoshop CS and later. While Illustrator does not have full LAB support as a document color space, it still can use LAB color definitions by using the Adobe Color Engine for color conversions to CMYK values. If these swatches are converted to CMYK values, the CMYK values vary depending on either the ICC profile assigned to the document, if the swatch is converted within the document, or on the printer ICC profile, if the document is printed.
Note: To improve onscreen accuracy, Illustrator uses the Lab values automatically if Overprint Preview is on. It also uses Lab values when printing if you’ve selected Simulate for the Overprints option in the Advanced area of the Print dialog box.
The PANTONE swatch libraries that reside in Photoshop use LAB representations of what the PANTONE ink will look like when printed using a spot color plate. When you apply the swatches to objects or duotones in Photoshop, Photoshop displays the color using the LAB color definitions. If these swatches are converted to CMYK values when printed, the CMYK values vary depending on the ICC profile you chose in the print dialog box.
In Illustrator CS2 and later, you can match the PANTONE swatches to Photoshop CS and later versions of the swatches by selecting the "Use LAB Values specified by the book manufacturer" option in the Spot Colors option dialog box. To access the Spot Colors dialog box, select Spot Colors from the Swatches panel menu.
In Illustrator CS, there is no way to automatically match the Illustrator PANTONE swatches to the swatches in Photoshop. The Illustrator swatches use specific CMYK color definitions provided by PANTONE, and the Photoshop swatches use specific LAB definitions.
If you are using the CMYK color definitions for PANTONE swatches in Illustrator, you can match PANTONE swatches in Photoshop to the ones in Illustrator by using the swatches from the PANTONE Solid To Process library in Photoshop. These swatches are designed to use PANTONE CMYK values.
If you are using the LAB color definitions for PANTONE swatches in Illustrator, you can match the PANTONE libraries in Photoshop by using any of the default PANTONE libraries, as they use the LAB color definitions as well.
You can match PANTONE swatches in Photoshop to the PANTONE swatches in Illustrator by using the swatches from the PANTONE Solid To Process library in Photoshop. These swatches are designed so that they use PANTONE CMYK values. The swatches in this library do not go through the LAB to CMYK conversion like the other PANTONE libraries, so they match the PANTONE swatches used in Illustrator.