If you cannot find the Accent key under Explorer, create one.
Open Registry Editor (Run > regedit), and navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Accent. If you’d like to change its background color, then it can be done from the registry, and here’s how.
Logon screen (seen below) is the interface where all user accounts are displayed. On Windows 8, you can easily personalize the lock screen image, system color scheme and the Start Screen background from PC settings, but Microsoft has not provided an option to customize the logon screen background colors.
