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.
Windows Settings/
Administrative Templates/
Local Computer Policy -> Computer Configuration -> Administrative Templates -> Control Panel -> Personalization
After changing group policy options, you need to update group policy. If you do not update group policy then settings will not effect. To update it just simply type below command and also sample image is shown.
gpupdate /force
In about command we used "/force" option, this will help up to update policy options forcefully.
