Hello! Amazing piece I felt super bad even painting over it. SO I personally would recommend painting a blue multiply layer and erasing the bits hit by light. Then, on another multiply layer with that same blue/little bit darker, hit the areas that are oclused by other objects or perspective. Then, a new overlay layer to paint, with a light blue or yellow depending on the light color (I went with a medium tone) and paint over the areas directly hit by light. After this, I would paint on another overlay layer the direction of the light (here I painted it to hit the characters directly) and then, on the first multiply layer, erase a bit of the darkness in the trayectory of the lamp's light. I think that's a pretty decent starting point! You could also add reflections to the windows which I completely forgot about ;; I hope this helps! I'm sorry if the explanation is a bit rough, it's my first time giving feedback | Artwod Feedback