Ignore chrome.css: go into about:config Set in the text field: toolkit.legacyUserProfileCustomizations.stylesheets = true

Find installation folder of Mullvad / Firefox / Librewolf about:support Go to Profile Directory | click Open Directory Create a folder called: chrome Create a file called: userContent.css

Examples where background is set to dark gray:

@-moz-document url("about:home") { /* Add custom styles for Firefox new tab / body { background-color: #1b1b1b !important; / Replace #yourColorCode with your desired color */ } }

@-moz-document url("about:welcome") { /* Add custom styles for Firefox new tab / body { background-color: #1b1b1b !important; / Replace #yourColorCode with your desired color */ } }

@-moz-document url("about:newtab") { /* Add custom styles for Firefox new tab / body { background-color: #1b1b1b !important; / Replace #yourColorCode with your desired color */ } }

@-moz-document url("about:preferences"), url("about:addons") { /* Add custom styles for Firefox settings or addon pages / body { background-color: #1b1b1b !important; / Replace #yourColorCode with your desired color */ } }

@-moz-document url-prefix("about:") { /* Style any about:* page, like about:config, about:support / body { background-color: #1b1b1b !important; / Replace #yourColorCode with your desired color */ } }

@-moz-document domain("example.com") { /* Add styles for all pages on example.com / body { background-color: #1b1b1b !important; / Replace #yourColorCode with your desired color */ } }

@-moz-document url-prefix("file://") { /* Add styles to local files / body { background-color: #1b1b1b !important; / Replace #yourColorCode with your desired color */ } }

@-moz-document url-prefix("https://example.com/settings") { /* Style specific paths like /settings / body { background-color: #1b1b1b !important; / Replace #yourColorCode with your desired color */ } }

@-moz-document url-prefix("about:home") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:newtab") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:welcome") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:preferences") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:addons") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:downloads") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:config") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:profiles") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:performance") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:plugins") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:support") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:logins") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:sync-log") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:blank") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:crashes") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:sessionrestore") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:memory") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:healthreport") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:networking") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:debugging") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:devtools") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:performance") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:telemetry") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:certificate") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:cache") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:permissions") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:robots") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:mozilla") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:blocked") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:networking") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:processes") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:policies") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:restartrequired") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:preferences#privacy") { body { background-color: #1b1b1b !important; } }

@-moz-document url-prefix("about:preferences#search") { body { background-color: #1b1b1b !important; } }

.sticky-container { background-color: #1b1b1b !important; /* Replace #yourColorCode with your desired }

#filter{ background-color: #1b1b1b !important; /* Replace #yourColorCode with your desired }

#handlersView{ background-color: #1b1b1b !important; /* Replace #yourColorCode with your desired }-