Do not allow color changes This policy setting controls the ability to change the color of window frames. If you enable this policy setting, you prevent users from changing the default window frame color. If you disable or do not configure this policy setting, you allow users to change the default window frame color. Note: This policy setting can be used in conjunction with the 'Specify a default color for window frames' policy setting, to enforce a specific color for window frames that cannot be changed by users.

(1) GPO: User Configuration\Administrative Templates\Windows Components\Desktop Window Manager\Window Frame Coloring!Do not allow color changes (2) REG: HKEY_CURRENT_USER\SOFTWARE\Policies\Microsoft\Windows\DWM!DisallowColorizationColorChanges