ColorfulTabs wouldn’t work at all until this Firefox bug is fixed: https://bugzilla.mozilla.org/show_bug.cgi?id=1320585

I’m lucky we got it to work at all. Currently we can only color the current tab. Thanks to Patrick for coming up with an innovative idea. Please also see: https://www.addongenie.com/forums/topic/colorfultabs-disabled-in-firefox-quantum. I'm working overtime to maintain this addon. So I don't mind you having to take a minute to create an account and give me a negative review.