One of the best features of the Google Home Hub is Ambient EQ. However, if you find that your Google Home Hub does not dim the screen in dark rooms, the feature itself may be disabled in a hidden menu in the Hub screen according to the ambient light in the room. When the screen saver is active, Color Matching will make photos look as if they were printed on paper and not on a display. When the backlight is off or off, the screen should be darkened automatically so it does not act as a bright flashlight in the room. This makes it the perfect device for your living room or bedroom.
All this is true unless Ambient EQ does not work, as in the photo above. The above Google Home Hub did not get darker after the first setup. A factory reset did not solve the problem. Environment EQ settings have not been disabled in the Google Home app. It turned out that the Google Home Hub has a hidden screen menu. And from here, the environment EQ can be disabled, overriding any settings made in the app.
So, if your Google Home Hub does not get darker, you'll first need to swipe up from the bottom of the screen. 
Tap the sun icon at the far left to display the brightness settings.
Tap the sun symbol on the far left.
 Now an A should appear in the sun symbol and the words "Ambient EQ on" should appear.
From here, dimming should work properly. This is a pretty simple problem that can only be fixed because the setting is not intuitive. If you set the brightness in this menu to a setting of 1-10, Ambient EQ is disabled.