HP OfficeJet Pro 7740 prints PDF files in color only, although black and white is selected in the print dialog

Hi folks,
I have a strange problem with my printer. In my home LAN I use the HP OfficeJet Pro 7740, a multifunction and wide format printer. In principle everything works as it should, but I can’t print PDFs in “Black Only Grayscale”, it prints these files in color anyway, even if I choose “Grayscale” as output profile. This affects the print dialogs in qpdfview and Firefox equally when I print PDF files. On the other hand, if I want to print a colored LibreOffice document in black and white, it works fine.

Nothing was changed in the default settings of CUPS or hplip. I installed the printer normally via hp-setup, and also installed the hp-plugin (I simply did hp-setup -i <my printer's IP> and hp-plugin in terminal and then set it as the default printer).
I use Manjaro XFCE, but also have the same problem in Arch XFCE. Is it possibly related to Ghostscript?

I’m still looking for a solution to this problem. Maybe someone has an idea…? :slight_smile:
Edit: With the free version of Master PDF Editor from the AUR, black and white printing of color PDF documents works surprisingly without any issues. Otherwise, the problem remains so far. I would suspect an issue with Ghostscript in connection with CUPS, but I am not quite sure.