It’s that way because Mozilla didn’t include any functionality in their new API to allow developers to do that. So they can’t fix Colorful Tabs.

It’s a really useful add-on and it’s hard not to see the Firefox decision as arrogant. When you have twenty Wikipedia tabs open, all showing the same W icon, but a third of them are from English Wikipedia, a third from French Wikipedia and the rest from Irish Wikipedia it’s a big help if each site’s tabs are a different colour.

It’s the same story apparently for Session Manager. Functionality dumped so the add-on can’t even be fixed. And that’s a very long-lived add-on.

Thank you so much for the candid, albeit frustrating reply. What Mozilla doesn’t seem to understand is that many of us stay with Firefox as a browser because we can use colorful tabs in multiple use situations. I might as well go back to Safari or use any other browser that has all white tabs. There’s no advantage here now. This is a very sad situation.

I'm all for change (sometimes), but when it goes backwards, it is counterproductive. I agree with the comments on this page.

These tabs are UGLY. Square, way too loooooooong, and no way to adjust size and shape. Whoever dreamt up this design, should go back to sleep and come up with a different dream.

Just sayin'  :(

I can't stand the new look and none of the themes fix the problems at all. I don't like the menu bar and tabs being the same color. I don't like the bookmarks toolbar being all the same color. Color lets our brain determine at a glance exactly the differences in a page and that can't be done now. I also can't tell what the active tab is easily.

The whole reason I have stuck with Firefox is how customizable it has been. Now they want us to have to crease css and all kinds of crazy stuff to be able to customize just part of the UI. It's ridiculous! The responses to complaints from other people that I've read saying the same thing is rude and unhelpful.

Mozilla has steadily and quickly removed so many of the customization options that there is no point in staying with it anymore. I'm absolutely disgusted with how little companies listen to their users. I can only hope that a new browser will pop up that remembers what made Firefox so successful for a long time which was that users could easily customize it FOR THEIR NEEDS.