Hi Cindy,
If the room is north facing it's worth adding some colour as a simple grey might be a bit depressing during the winter time. The best colours for a bedroom are blue and/or beige as they help you to sleep better. Try to find a warmer shade of blue, then you can combine it with some nice bedding and curtains. You can try to add monochrome or grey shade patterns. There are also loads of "coloured" grey shades with a bit of blue or purple that look more interesting and certainly warmer too.
The colours to avoid are orange, yellow and red because the northern light is blue(ish) and it will add a cool blue tone onto everything in the room - this makes the above mentioned colours look awful.
Hope this help! It would be nice if you could update this thread when you're ready so we see what you choose :)
Q