We must be rule breakers! LOL! Our master bedroom faces north and is painted in the cool-calm-and-comfortable Silver Sage from Restoration Hardware -- with bright white trim. Love this color -- and it goes with so many other colors including black and white decorative accents! The furniture is deep walnut but there is both silver and gold accessories and accents around the room. The adjoining bathroom is painted in bright white with dark sage green towels. You could simply add a touch of warmth in your bedding colors -- perhaps a red or orange. Or add color with warm colors in the artworks. Hope this helps! It is a photo of our bed -- with its winter bedding. In the summer we use Ralph Lauren's "Sussex Gardens" comforter and shams (with a peachy background and florals) with a leaf-green or very old soft orange-peach satin comforter folded at the bottom of the bed.

What's outside your window? If there's a lot of foliage, it will eflect green back into your room and change any any color you paint the walls. Ditto a red brick wall. What is your climate? In the south, blue in a north-facing room would be refreshing; in the north in winter it could be downright chilling. A cream, blue, or even soft pink could work well, but you should probably choose your fabrics before your paint. It's easier to match the paint to the bedding than vice-versa.

I just painted my north facing room smokey taupe from Benjamin Moore. I tried BM Halo on poster board in the room and looked at it from all different angles and at all different times of day and thought I loved it. When the room was painted it looked mint green. I had to then make a decision about what color to repaint and snow made it so I couldn't go get samples -- so I did as much research as I could on other "grieges" and picked smokey taupe from a paint strip because the articles I found said it had red undertones versus green -- and I love it. Has a nice taupe-gray feel that's very neutral. The upshot is, pay attention to what research you can find about undertones -- I don't recommend picking from a paint strip, obviously, but the research helped a lot (and I guess I got a bit lucky). I know seeing is believing, but a little supplemental research can really help, too. Wish I had paid attention to it before I had to repaint!

I don't have any color suggestions, but...you can't accurately see the colors when they're painted on top of a colored wall. You can get some poster board, cut it in quarters, and paint those (maybe pick your top few colors from your samples) and set those against the wall in various parts of the room and look at them at different times of day. Make sure they have white behind them (another piece of posterboard) so you can see the colors accurately and not have the current yellow wall color change them.