Katherine, you may be better served asking a designer than a photographer, but since you asked... The main thing is keeping a sense of flow. You may want to find a general style that works for you (contemporary, post modern, country, traditional, etc) and base your choices on that "feel". I have been in homes where rooms were each totally different colours and its worked, but its a tough balancing act in trying to maintain a sense of continuity and flow. Again, that's been my observation but you would be best served to ask a designer.