I've come to the conclusion that pretty much anything paired with a navy blue jacket will look somewhat professional. Case in point, my shirt today is reasonably loud and my skirt is very pastel. The jacket completely tones down the look.
I am really loving Gap's blazers right now. I've purchased this particular style in probably four or five different colors. Of course, this was after the closet purge and I told Dave I wasn't buying any more jackets!