Enter about:config in the address bar and set ''layout.css.prefers-color-scheme.content-override'' to '''1'''. <i>'''WARNING: Changing preferences through this interface not officially supported''' Hidden settings edited using the about:config tool are explicitly not supported, which means that Mozilla makes no guarantees they will be supported in the future, or that Mozilla will fix them if they break. Mozilla does not test these preferences, and will not in the future. That includes security and performance testing which these preferences may affect. </i> ''[Warning added by moderator.]''