I switched to painting all my hive boxes black after seeing you do it. Some people, as usual, think I'm crazy, but I don't think it harmed the bees at all. It just doesn't get hot enough on the east cost of Newfoundland for the black boxes to cook the bees or do harm.
I don't wrap all of my hives in the winter because they're in sheltered areas, and I think blank paint allows them break cluster a little easier when they need to. That's my theory anyway. I know some "condensing hives" argue that temperature fluctuation that cause the bees to break cluster and cluster again stresses the bees, but I'm no convinced of that yet. In any case, the black paint has worked out well for me.
Have you considered trying out poly hives in your area? I'm still experimenting with one that I've had since last year, but other beekeepers in my cold climate similar to yours rave about them. They don't require wrapping or any kind of winter prep, the bees don't eat as much honey and they brood up quicker in the spring. Or so I'm told. My first winter with a poly hive, last winter, wasn't a good test because I had an old queen who was fading fast going into winter, and the colony petered out by the spring, which I don't blame on the poly hive. But I'm hopeful.
