Backup the registry before proceeding.
Steps:
1. Press Win Key or Win+R Keys, then type regedit.
2. Go to HKEY_CURRENT_USER
3. Locate "Control Panel" > click "Colors" > then navigate to "Window"
Default value is 255 255 255 which is white.
4. Change the value to your desired color. E.q.: 192 192 192 for grey
5. Restart the station
Path:
Computer\HKEY_CURRENT_USER\Control Panel\Colors
Reference: RGB Color Codes Chart 🎨 (rapidtables.com)