This post summarises it nicely: Push a solid colored background to a Windows Server 2012 or later | Tidbits of Information from Virot.
I already knew about the one below, but the post above gives a more complete picture with:
- Background color
- tells how to set the menu and
These I already knew:
- “HKEY_USERS\.DEFAULT\Control Panel\Colors” Background.
- “HKEY_USERS\.DEFAULT\Control Panel\Desktop” Wallpaper.