How to turn off the LED light on the Viewsonic VX2718-PC-mhd monitor?

«Setup Menu» → «Power Indicator» → «Off»

Set the Power Indicator On or Off.
If the setting is set to On, the power indicator lights blue when the device is turned on.

manuals.viewsonic.com/VG2440V_On-Screen_Display_Menu_Options#Setup_Menu