Force a specific background and accent color
Supported on: Windows Server 2012 R2, Windows 8.1 or Windows RT 8.1 only
Registry
HKLM
Software\Policies\Microsoft\Windows\Personalization Options
PersonalColors_Background text PersonalColors_Accent text Description
Forces Windows to use the specified colors for the background and accent. The color values are specified in hex as #RGB. By default, users can change the background and accent colors. If this setting is enabled, the background and accent colors of Windows will be set to the specified colors and users cannot change those colors. This setting will not be applied if the specified colors do not meet a contrast ratio of 2:1 with white text.