got a HP Color LJ 1600, and the colours are not great. Searched the web, found pages about improving colours for 2600n (referenced from OpenPrinting database - Printer: HP Color LaserJet 1600). Set gs to point to gs-gpl version 8.54, verified that it's used, also tried the km2430_2.icm profile, nothing changes anything.

To powder consumption - it does do colour calibration after each power on after being idle for some time and I didn't find the option I have to switch off as described in foo2zjs | foo2hp | foo2xqx | foo2lava :: View topic - Excessive color tonor usage hint - is it all only relevant for 2600n and not 1600?

As for 1600 here foo2zjs | foo2hp | foo2xqx | foo2lava :: View topic - status of driver they say to use directions on foo2zjs.rkkda.com, but there's also nothing I could directly identify as relevant... first it doesn't even mention 1600, second in the "Color Correction" section it only tells about "CRD-based method" but doesn't say how to use it...