Just a note that there is another thread on this, in case any of the discussion there is relevant: https://support.mozilla.org/questions/1417523

Yes, changing colors on activate/deactivate is annoying for me too. Looks like both issues are caused by the same changes in browser/themes/linux/browser.css.

After Firefox upgraded from 114.02 to 115 menu and tabs background color changed: FF 114: https://assets-prod.sumo.prod.webservices.mozgcp.net/media/uploads/images/2023-07-05-17-00-30-1a3adf.png FF 115: https://assets-prod.sumo.prod.webservices.mozgcp.net/media/uploads/images/2023-07-05-17-00-34-cba7e0.png These are screenshots of active window. When window of v115 becomes inactive, background color changes to lighter, but still no visible horizontal line between menu and tabs. I don't use any additional themes, "System theme — auto" is selected. From release notes for FF 115: For users with a Firefox Colorways built-in theme, the theme will be automatically migrated to the same theme hosted on addons.mozilla.org for Firefox profiles that have disabled add-ons auto-updates. This will allow users to keep their Colorways theme when they are later removed from Firefox installer files. I guess it is relevant somehow, but i never installed Colorways and don't know what is it. How to make FF 115 look like it was in 114? I can see changes in `browser/themes/` in sources between 114.02 and 115. Is it possible to "extract" default theme from 114 and install/apply it to 115? I use Firefox under Fluxbox window manager in Arch Linux, if it matters.

Switching themes will make the issue go away. In fact, that's exactly what I did as a temporary solution. I've tested many themes. As far as I can tell, only the "system auto" theme is affected. It's so damn annoying.

These issues can be worked around using userChrome.css

To fix the background colour:

``` vbox#titlebar {

   background-color: InactiveCaption !important;

} ```

To bring back the line above tabs:

``` tab.tabbrowser-tab {

  border-top: solid #ccc 1px !important;

} ```

All of this will probably break in the next Firefox release. Updating userChrome.css is turning into a monthly ritual for me.

These issues can be worked around using userChrome.css

I created `~/.mozilla/firefox/<profile folder>/chrome/userChrome.css` with following content: ``` @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

vbox#titlebar {

  background-color: InactiveCaption !important;

}

tab.tabbrowser-tab {

 border-top: solid #ccc 1px !important;

} ``` but don't see any effect, unfortunately. Also tried to move `userChrome.css` directly to profile folder, the same.

Just FYI, this forum software doesn't understand ``` to mean "code block". You can use <pre> before and </pre> after code to reduce the risk that it gets corrupted:

vbox#titlebar {
    background-color: InactiveCaption !important;
}
tab.tabbrowser-tab {
   border-top: solid #ccc 1px !important;
}

a.j.buxton said

These issues can be worked around using userChrome.css

I created `~/.mozilla/firefox/<profile folder>/chrome/userChrome.css` with following content:

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

vbox#titlebar {
   background-color: InactiveCaption !important;
}

tab.tabbrowser-tab {
  border-top: solid #ccc 1px !important;
}

but don't see any effect, unfortunately. Also tried to move `userChrome.css` directly to profile folder, the same.

Using a chrome folder is correct. Make sure that you toggled toolkit.legacyUserProfileCustomizations.stylesheets to true in about:config so that Firefox will look for the file at startup (this is required in Firefox 69 and later, so older instructions may be incomplete).

Also, I recommend NOT using a namespace line because Firefox's UI is a mix of XUL and HTML elements.

P.S. I haven't researched what these rules do. If you aren't noticing a difference, you can substitute highly visible color keywords like red or yellow for testing.

Using a chrome folder is correct. Make sure that you toggled toolkit.legacyUserProfileCustomizations.stylesheets to true in about:config so that Firefox will look for the file at startup

With toolkit.legacyUserProfileCustomizations.stylesheets enabled userChrome.css it does work. Thank you.