It's safe to leave it, but if the plug /outlet is handy I would just unplug it from the wall.
Even on standby it uses a little bit of power.
maybe the monitor on/off button is broken or funky...

Or if everything is plugged into a power bar/surge protector- which is a good idea - then just turn off the power bar or unplug it.

A month is a long time to have that amber light glowing for no reason..

They should know how to unplug something from the wall, right??
*unless it's really hard to get to the outlets because of heavy furniture or clutter* then I'd just leave it as is.