As the editor stands at the present it is not possible to turn off the blue light at all once darkness falls. There seems to be a built in set up in which any flashing light, be it blue or yellow (as for hovercraft) stays on permanently in the hours of darkness. This causes, for example, the blue light on "Arie Visser" to remain flashing even when she is moored or towing another vessel. Thus of Martys 3 conditions above, as he points out, only condition 1 is valid for version 1.4.2, build 1038.
Regards,
Angus.
Attached picture below shows Hovercraft & Arie Visser, both moored with navigation lights off, but flashing lights remaining on.