I am a bit of a clean freak. White. All my hives are white, it means to me pureness. I don't think there is anything more beautiful in this world than white, anything. I love colours though, don't get me wrong. Besides, I can see EVERYTHING with white hives. They stand out, in twilight and dawn, and even on a beautiful moonlit night. White reflects light, keeps the hives cooler than a dark colour, like Finsky says. Cool hives, keep the colours light. Period.
With white hives, I can see very clearly from a distance if there is a problem with too much heat, swarms emerging and so on, it allows to see what is going on around the colonies. Bees are dark and show up clearly against white background. White I shall stick with. If I wanted a little bit of colour just to spice things up, I would still leave the brood chambers white, the honey supers a different colour. My opinion and preference.
I like to paint a little picture on each colony's box, usually just a circle or square, in a different colour, just for fun, and maybe it helps the bees to orient to their own hive more easily, maybe, it probably makes for a better "target" for them when they come home weary and heavy from some hard work. LOL.
Have a great day, enjoy 2007. Cindi