DeviceLoginScreenDefaultHighContrastEnabled

Setting the policy to True turns High-contrast mode on at the sign-in screen. Setting the policy to False turns High-contrast mode off at the screen. If you set the policy, users can temporarily change High-contrast mode, turning it on or off. When the sign-in screen reloads or stays idle for a minute, it reverts to its original state. If not set, High-contrast mode is off at the sign-in screen. Users can turn it on any time, and its status on the sign-in screen persists across users. Note: DeviceLoginScreenHighContrastEnabled overrides this policy if the former is specified.