This is ongoing, including adding some more UX options
- this is an issue where a new tab “flashes” the letterboxing color whilst awaiting a the site to load. There is no easy answer here (and it would apply to the letterbox color shown around the sides) as to what color to use, but see below
privacy.resistFingerprinting.letterboxing.gradient is a pref (not exposed in settings yet), to enable/disable the gradient
There is talk (can’t find the issue/link) of adding a UX to set a solid color of the user’s choice - that way if you want it to be dark, or light, or bright barbie pink, that’s up to you