So my librewolf config has 23 color-coded containers with rules for various websites I use.
Which actually, maybe it's just my OCD because that's probably possible with the different icons for the stock multi-account containers add-on. But I made mine be all just the solid circle icon and a unique color for each because I wanted it color coded. Which I guess is a little OCD brained but
Also made the letterbox black.
If anyone's interested I can share the mods
They don't. Neither does Windows AME.