RGB palette to predetermined CMYK palette in InDesign and/or Illustrator

Question

Happily this isn't yet another "why do my RGB colors look different in 4cp output" question. But let me admit that I may be missing something obvious here.

I am working with InDesign and Illustrator documents that adhere to a brand-defined palette of various RGB colors. The documents are mainly intended for web viewing and download via PDF. However, some will now be printed via offset/web/digital.

I know InDesign and Illustrator can convert RGB documents to CMYK for print output; however, the design language here also defines the brand colors in predetermined CMYK colors. These were determined kind of arbitrarily based on a press check someone did long ago looking at what CMYK swatches on coated paper appeared closest to the RGB brand colors seen on-screen.

So I know that if I output to PDF with convert to US Web Coated (or whatever the vendor wants if not that), the final print output will look preeetty close to our CMYK swatches but not exactly. I'd like to get it exact. By adhering to the "correct" CMYK values, and so I want to swap out the RGB swatches with the CMYK swatches without resorting to any kind of color profile stuff. (Or—do I in fact need some kind of custom color profile stuff? This is not what I understand them to be intended for)

In Indesign, the only way I can think of to do this IN the source file is importing the CMYK palette, then deleting the RGB colors one by one from the document and replacing with the equivalent CMYK swatch. Or some even more onerous process in Illustrator. There are a lot of colors and a lot of files so want to avoid this.

So the problem is I can't think of or find a way to automatically map the RGB values to those assigned CMYK equivalents. Either in the source file or upon output (either way would work for me—although it would be nice if I didn't have to start maintaining two versions (RGB+CMYK) of each source file). In any case, is there some method or script or plugin to swap the RGB swatches with the assigned CMYK swatches programmatically?

Or is this something we should be asking the print vendor to do for us? (this seems doubtful).

Answer 1

This might be a non-answer, but my honest advice for you is:

Don't do it this way.

• As you are realizing, this method is really cumbersome and time consuming. It could be scripted, as @joojaa mentions, but custom scripts shouldn't be necessary for such a common task of matching screen colors to print colors.

• CMYK colors are not absolute colors. They are a set of "instructions" for the printing device on which halftone percentages to use. The resulting colors can look dramatically different when printed on different media using different printing devices. CMYK profiles have been invented to avoid this problem.

• The CMYK values you are given were made using some specific printing device on a specific kind of paper. They were compared to a specific screen. Are you going to use the same printing device on the same kind of paper? Was the screen color calibrated to live up to ISO standard? Did the lighting in the room live up to ISO standard or could it have been warmer or colder?

• The darkest swatch you have has a total ink coverage of 300% (all four inks added together). This might be fine for coated paper, but on other kinds of paper you might need a lower coverage to avoid smearing and other problems. So you would have to manually tweak the darkest colors. Color profiles takes this into account when converting your RGB colors to CMYK.

In my opinion, your best bet is to convert the RGB colors to the CMYK profile recommended by the print shop on export (no need to manually convert each swatch). This should ensure the best possible color likeness to what you see on screen (provided that your screen is correctly color calibrated, that the print shop adheres to the color profile they specify and that the final print is viewed under the correct viewing conditions).

Converting from RGB to CMYK is done all the time when preparing images for print. The graphic designer adjusts the images on screen until a pleasing result is achieved and trusts the color profile to reproduce these colors on print as well as physically possible. Why should a different method be used for color swatches?

You seem to be worried that the CMYK values you get when converting aren't "exact", but as I mentioned above the values you are given are only "exact" for a very specific situation.

When likeness to the brand colors is important, you should spend a little extra money on a proof, so you can check if the colors look as they should. You could even get a proof made where you compare the "old" CMYK swatches you have been given with the same colors automatically converted from RGB to the correct color profile. This might give you some assurance before doing the final print.

Answer 2

Make a copy of your RGB colors put it in a folder called colors in document. Use only these colors. You can then drag the symbol swatches form one set over to anothers icon and it overwrites the swatch updating all globally assigned colors.

Now in illustrator you can just record an action overwriting one to another. But you could easily just script this process. Good first project, just a for loop really.