Some colors are not printed on B/W IPP Everywhere printer

Dear devs,

I have a problem with my Brother HL-L2370DN printer. It's a B/W duplex laser printer. I configured it as an IPP Everywhere printer, as one does nowadays. For a year or so, no problems. Recently, it stopped printing red text. Everything else was there, but the red parts were simply omitted. Until then, they appeared in a dark gray tone.

I'm on Gentoo Linux, using CUPS 2.4.7. I'm not sure which update triggered the problem, and if it actually was the CUPS one, as it could be a month until I noticed it.

However, if I talk to that printer using the Generic → IPP Everywhere driver, the color wheel on the test page looks like this: and some text containing a red line looks like this:

When configuring the printer to use the brlaser driver it apparently also can use, the relevant part of the test page looks like this: and the text test like this:

I also tried to print from a Windows 10 VM, that has never been configured to print. It found the printer and apparently chose to use IPP Everywhere without any interaction. The same test with the text lines and one being red yields comparable results like the one printed with brlaser.

I also tested to print from a notebook running Artix Linux. It also runs CUPS 2.4.7, and red text isn't printed as well. I'm pretty sure that in the past, I could also "normally" print from the Artix machine.

So I think this is not a Gentoo-specific issue, and apparently, it's also not a problem with the printer itself. Apparently, something is currently wrong with the conversion from color to grayscale?

I would really love to track this down and help getting this fixed, as all the new printers use IPP Everywhere!

Cheers, Tobias

apple / cups

Some colors are not printed on B/W IPP Everywhere printer #6190