Gate Agent reported B787 door window remained dark; requiring the Flight Attendant to use a flashlight to improve visibility and allow the passenger door to be opened.

Narrative

I was meeting Aircraft X; ZZZ to ZZZ1; a 787-8; at gate XX. Operation of the jet bridge was normal; but when I went to do the safety check - knock on the door - I noticed the window was blacked out. I could not see the indicator light. I knocked several times; and while doing so I contacted Zone 1; by phone; but no answer. I finally reached Zone 2 and spoke to the Supervisor. Finally; a Flight Attendant shown a flashlight into the window giving me the indication that I could open the door. After opening the door; the Flight Attendant informed me that all the door windows were blacked out. The window remained dark; and towards the end of the deplaning; the window finally turned to a lighter color. The Flight Attendant was the hero; using her flashlight to communicate with me that the door was safe to open. I did ask the Purser about the situation and she said that the windows were in the landing mode and they were not in the nighttime mode. I reported the situation to Supervisor and to Ops.