When planning a neutral room it's normally important to have some bolder colors in small doses (as flowers, a framed photograph, a ribbon on a pillow) to keep the room from becoming blah. In this case, the color comes from what's outside the window. High rises and the city outside become the everchanging pop of color. When it gets to be too much, just close the curtains.
So when you are planning a room, don't forget to look at what colors are a part of your palette just from being outside of the window. Do you have tons of lush green plants? A brick wall? Someone's colorful laundry? Rooftops?
Could you live in such a neutral bedroom? Is the cityscape enough color for you or would you need more?