After my interesting journey into replacing greyscale values in the vector PDF export of Onyc BOOX Notes, some brainiac on Mastodon pointed out that there are non-grey colors I could use. (Seriously, thank you Jeroen :))

So the solution is to simply use colors, not shades of gray!

That’s even less work for me, which is good, but I’m still a bit sad that the PDF recoloring experiments have now ended.