Bugzilla

> I'll point out too that Chrome also has this problem on my computer. 

So you're right - when it's active, at least, there's a grey bar on the right and the bottom side but not the top and the left side...?
However, when the window is inactive, the grey borders seem correct.

This actually bug goes away for me when I check the box in Windows' Personalization - "Show accent color on the following surfaces" - "Title bars and window borders". This show the top border with accent color when active, and grey color when inactive, like the rest of the sides, as expected. However, there still are some oddities:

* When Windows using the light theme, the top inactive border is noticeably darker.  
* When switching Firefox in and out of the active window, I sometimes see a visible delay in the top border being painted the accent color.
* Turning off the accent color leaves Firefox's top border to be that accent color, but only when it's active (Reverts to missing top border behaviour on restart).

> I'll point out too that Chrome also has this problem on my computer. 

So you're right - when it's active, at least, there's a grey bar on the right and the bottom side but not the top and the left side...?
However, when the window is inactive, the grey borders seem correct.

Actually, the bug goes away for me when I check the box in Windows' Personalization - "Show accent color on the following surfaces" - "Title bars and window borders". This show the top border with accent color when active, and grey color when inactive, like the rest of the sides, as expected. However, there still are some oddities:

* When Windows using the light theme, the top inactive border is noticeably darker.  
* When switching Firefox in and out of the active window, I sometimes see a visible delay in the top border being painted the accent color.
* Turning off the accent color leaves Firefox's top border to be that accent color, but only when it's active (Reverts to missing top border behaviour on restart).