If you do a google search there is a Addon called Firefox Colors but that isn't created by Firefox/Mozilla itself. If that's the Addon then you need to go to their homepage and contact them about their Addon issues.

If you do a google search there is a Addon called Firefox Colors but that isn't created by Firefox/Mozilla itself.

Actually it is a Extension from Mozilla as Mozilla does have some official extensions of their own listed on addons.mozilla.org though most extensions listed on AMO are made by a third-party author or company.

I have this problem too, it just broke a week or so ago. If I load in my own settings or pick one of the preset themes, they do apply during that browser session. But if I quit FF and relaunch, the profile will flash briefly to what it's supposed to be and then change back to the default.

Here is an MP4 showing me launching it a few times with one of the preset themes set (top middle, the dark blue-green one): Screen Recording 2024-11-02 094412.mp4

In the movie the first and 3rd time the flash is quite fast so you'll only see the tab bar start turning light blue before it goes back to default grey, but on the second time you'll see the tab bar and the toolbar start to change before changing back.

You can check the Firefox Color reviews for some possible workarounds to try.

• https://addons.mozilla.org/en-US/firefox/addon/firefox-color/reviews/

from https://support.mozilla.org/en-US/questions/1472451#answer-1685593

Oh wait. I was able to go back into the Settings --> Themes and then change it to the Custom Background.

Firefox 132.0.1 should help fix the issue with Firefox Color extension.

https://www.mozilla.org/firefox/132.0.1/releasenotes/

Fixed an issue causing themes to reset to default after restarting Firefox, in particular when using the Firefox Color add-on.