Windows 10/11 has changed the color of the active and inactive Title bar. Some applications may overlap when multiple windows are opened. Users may be used to the color scheme from Windows 7. What about that? (This problem also occurred to a lesser extent on servers operated as RDP/Work resources (W2012-W2022).
Changing only the Title bar is not a problem, I also remove the background image.
Download e.g. ClassicThemeForWindows10
Extract example ClassicThemeForWindows10/Theme For Win10 April 2018 Update 1803/Show Commandbar/ to c:\Windows\Resources\Themes\
Go Start > Settings > Personalization > Themes.
Apply Dark or Light theme (I prefer dark).
Go Personalization > Colors.
Turn off the option „Show color on Start, taskbar, action center, and title bar“.
Turn off the option „Automatically pick an accent color from my background“ if enabled.
Turn on Title Bar and borders.
Now, pick a color you want to apply to the title bar of inactive windows. (yes, we set the color of the active window, but we need it for the inactive :-))
Next we will work with Registries.
Go in HKEY_CURRENT_USER\Software\Microsoft\Windows\DWM
Create value „AccentColorInactive“=dword
Copy value from AccentColor to AccentColorInactive.
Set a new value for the foreground color. (in Personalization > Colors.)
TotalCmd, 2 windows across each other, active and inactive window.
after the change