Just found C0, M100, Y100, K10 as the appropriate value on the web, and could of course make up my own, but my gut feeling tells me there’s got to be Cyan involved?

Indeed, if you combine 100% of magenta with 100% of yellow and 10% of Black, the result will be closer to red than blue.

Do you have Adobe Photoshop or Illustrator at hand? Or Adobe InDesign, or QuarkXPress? Because their color palettes will allow you to select a Pantone color and then break it up into CMYK values... And the results will be true blue! (Pardon the pun... I couldn't help myself.)

Franz:

Google "Pantone Color Bridge PDF".

Pantone has released a PDF soft copy version of the Bridge. You can find it within the first couple results.

Cheers,

Kyle

M91, Y76, K6

Many thanks to all of you. Just installed the color bridge libraries. They come up with 2/100/82/6. Will again double check tomorrow (in daylight) with general 4C charts. Thanks again, everybody.

I'm sure Pantone Color Bridge is more accurate than the Photoshop/Illustrator option I suggested.

Cheers and good luck tomorrow,
R.

Thanks again everybody, the outcome was the probably best possible: I succeeded at convincing the client last minute to just use an additional spot color – Pantone 186 C. It's good to know there's a place with a lot of helpful people aound like this, in case things get rough. Thank you all.