Hello,
This may be an implemented but undocumented feature, but PGF does not seem to provide a method to control the colour model used for output. It is hard to see how to get CMYK colours used in the output without using low-level colour setting macros.
Joseph Wright
This may be related to https://sourceforge.net/p/pgf/feature-requests/29/. There's some deep magic that prevents CMYK from working properly with all the backends, and therefore this has been on the back burner. I don't pretend to understand the details, though...
~ben
Last edit: Stefan Pinnow 2018-12-31