Forum response -Settings for themes
Settings for themes will default back and will need to be re-enabled:
- Visit https://addons.mozilla.org/firefox/themes/.
- Click on the theme you want to install.
- Click the Install theme button. Click Remove if you change your mind. Your changes will apply automatically.
See Use themes to change the look of Firefox or Built-in themes in Firefox - alternative to complete themes to learn more about themes.