I generally follow this rule (hence, my BM Pale Smoke Living area and BM Silvery Blue Kitchen) but I am considering going bold when it comes to my petite bathroom.
SYMPHONY BLUE is the color I am contemplating. The color was featured on a Domino magazine cover with Zooey Deschanel as well as in a Lonny magazine spread. Granted, in both places the color was used in a somewhat larger space than my bathroom but it is so cheerful and I think with some black and white vanity fair portraits, my white marble tile and possibly a white (or gold or brushed nickel or floating wood...another element to obsess over!) mirror, the color would end up really being an accent and not engulfing the room.
Alternatively, I could go the safe route and paint it all cliffside gray/marilyn's dress (*both Benjamin Moore as well!)