North facing living room

I would be looking at a light duck egg blue but everyone’s tastes are different. Certainly have a white ceiling and light walls to maximise the light.
I have a bay windowed north facing dining room and we had grass at the front which proved very difficult to stop the moss taking over so we removed the grass and replaced it with white stones. We couldn’t believe the difference it made to the dining room.

If you have grey and blue I would introduce some yellow. With a north facing room just having blue and grey will make it feel a bit cold but yellows bring in brightness and warmth. Blue, grey and yellow look lovely together.