Description of the new feature/enhancement

Context
When working on large monitors it is possible to have up to 6 windows in tiled mode. It is useful to know which one will pick up the keyboard actions without mouse or alt-tab hunting. For that it would be useful to have a different title bar color for the active window to distinguish it from all the other windows.

Solution on Windows
One can pick a color for the active window (HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\DWM\AccentColor, say soft blue, can be done through settings)
and a color for inactive windows (HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\DWM\AccentColorInactive, say light gray, in windows 10 can be done through regedit only)

Applications that work with the two values above: Windows Explorer, Registry Editor, Total Commander, Mozilla Firefox (default theme), Google Chrome (default theme).

Terminal seems to not work with the two values.

That may be at odds with the application identity. (The discontinued Microsoft Edge 44 used the same gray as a strong identity element, Microsoft Office programs also boldly state color identity and ignore AccentColorInactive, VSCode states identity as boldly, however it displays the titlebar in a different color when inactive).
Nevertheless, screens only get larger and the use-case described above is likely to become more common.

In terms of how to implement that for Terminal, which displays tabs on the title bar, Firefox has the solution of using the accent color on all inactive tabs and highlighting the active tab using a brighter color. Chrome does the same.