(Copying this over from the Ideas site.)
Windows provides users with the ability to customize an accent color for window titlebars.
Firefox should support this accent color for the tab strip.
On Windows 10, the option is enabled under:
Settings > Personalization > Colors > Show accent color on the following surfaces > Title bars and window borders
The color for inactive windows can also be adjusted via the registry, and Firefox should also use that color when it has a value to support better accessibility.
For what it's worth, the default theme on Linux Firefox is derived based on the GTK theme, I don't see why the Windows version shouldn't incorporate the Windows Them Color as well.
Windows version color is not available
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Yes please! The accent colour helps identify which window is focused/active.
Both Chrome and Edge utilise the Windows accent colour (with dark theme too) support this, BUT their title bars remain coloured, even when they're inactive, which is non-standard:
The only clue that Firefox is the focused app is a very fine 1px border (which doesn't show when maximised):
Hard to understand that it needs a bugzilla entry (with many dupes) and an "idea" with many votes to (hopefully) finally fix something again that has willingly been broken...
@JonWhat do we need to do to get this promoted from "Trending" to "In development"? This had hundreds of votes on the old Crowdicity site, and that Bugzilla link above is 2 years old. It's incredibly frustrating to see other ideas with way fewer votes getting development priority above this.