In the latest version(s) of FireFox (using 57.0.4 on Windows 10), the only way to customize the color of any of the internal pages (the about:newtab, about:preferences and all addons related pages - both about:addons and all pages under https://addons.mozilla.org/) seems to be via changing the FireFox "Colors" preference. Due to my vision problems, I want to have all internal FireFox pages have a black background with white text (instead of the default glaring white with grey text). I also run a high contrast theme under Windows. Since the default FireFox colors preference just doesn't cut it on most web pages (it e.g. also removes all background images, making most graphical buttons on websites show just an empty border), I already use the extensions "Dark Background and Light Text" and "Invert Colors". But due to the new FireFox WebExtensions limitations these can only work on regular pages and not on these internal pages. Setting the global color preferences impacts the ability of these addons to work, so that is not an option for me. I already hacked a userContent.css file together to at least change the about:newtab page's colors, but the result is far from perfect (you can't get away with a simple background/foreground color setting; "#onboarding-notification-bar" and ".context-menu-list" elements also need color changing, and then I'm still getting a glaringly white infobar at the bottom of that tab). But that leaves all other internal pages hard to use for me. Like e.g. the about:config page, or the default glaring white chrome color that flashes by before the about:newtab page shows... What are my options? Do I really need to add CSS for all these internal pages separately, possibly also adding code for any extra elements which seem to have hardcoded styles as well? Or is there some other more global CSS selector I can use? I've also tried setting the hidden "privacy.resistFingerprinting.block_mozAddonManager" setting to True, but I think at least the "Dark Background and Light Text" extension doesn't even bother anymore to do anything on internal pages (it says so when trying to use it on such pages). Or is a fork of FireFox which doesn't have any of these restrictions my only option?