Did you change the theme setting in the Web Developer toolbox settings (cogwheel on the Web Developer toolbar) once you have chosen the light theme in about:addons appearance?

That should work for the developer tools only.

cor-el said

Did you change the theme setting in the Web Developer toolbox settings (cogwheel on the Web Developer toolbar) once you have chosen the light theme in about:addons appearance? That should work for the developer tools only.

I already tried that. However, I tried it again, but it didn't work. :( I have also gone to about:config and set lightweightThemes.selectedThemeID from firefox-compact-dark@mozilla.org to firefox-compact-light@mozilla.org but when I restart Firefox, it resets to whatever the developer tools theme was.

I hadn't tested it with a lightweight theme, but I can confirm that what I posted only works when the default theme is selected. Once you select compact light or compact dark then this applies to the Firefox user interface and to the Developer Tools. You would have to use code in userChrome.css to style the user interface and use devtools.theme = dark for the developer tools.

• chrome://browser/skin/compacttheme.css
• https://dxr.mozilla.org/mozilla-release/search?q=regexp:compacttheme.css