These are steps to adjust screen brightness as well as Day/Night modes
To adjust the screen brightness, use the dimmer buttons on the left side of the screen display (above the PWR button). The screen will brighten (+) or darken (-) a shade each time you press. Press multiple times if necessary to reach the desired brightness. You can also adjust the screen colors for better visibility as lighting conditions change. Touch Setup, Screen Colors, and choose from the following options:
Day: The default setting (original factory setting).
Night: Uses a darker color palette to portray chart details and controls. This darker color scheme helps preserve your night vision by keeping the display just bright enough for nighttime use, so your eyes don't have to adjust between a bright screen and dark surroundings. (During daylight the Night scheme may look almost completely black, but try it at night and you'll see the difference it makes.)