By the time you add on all the junk you want to have for commuting (lights, racks, fenders, panniers, etc.) and ride in the rain a couple of times, most bikes already look ugly. (dirty helps). I have a black bike that looks really crappy when it's dirty (it usually is this time of year), so I don't have to take any further uglification steps. I lock it when I park it in public, anyways.