Hi. Excellent idea. Help to know the container that we are active. The text of the tabs, of the navigation bar and of the bookmarks bar has the text format in bold and with shadow. It is difficult to read, better without shadow. It is the same when viewing the text in tree style tab. Thank you! regards

Great and very useful idea! But why by default (without container) it apply dark theme, instead of default firefox theme?

Also will be good to see more detailed description and screenshots.
And please describe here differences between your extension and https://addons.mozilla.org/ru/firefox/addon/containers-theme/

Very helpful add-on to visually distinct between different containers.