Diagnosis
The white/blue LED power indicator on the front bezel can be disabled through the On-Screen Display (OSD) settings. It is a software control.
How to Fix It
Press the physical button on the bottom-right rear of the monitor to open the OSD. Navigate using the joystick. Go to the 'Others' menu (the icon looks like a page). Select 'Power LED'. Change the setting from 'On' to 'Off'. The light will turn off immediately.
If That Didn't Work
If the 'Power LED' option is greyed out, you may be in a preset display mode that locks some settings. First, go to Display > Preset Modes and select 'Standard'. Then return to the 'Others' menu to access the Power LED setting.
Heads Up
With the light off, you will have no visual indicator that the monitor is in standby versus powered off. Listen for the relay click when you press the power button, or look for a faint backlight glow in a dark room to confirm it's on.