If the hives were metal, blackbody radiation would have great
effect, but wood- not sure. My guess is that heat transfer
through the wood would have little effect compared to air
intrusion from the entrance hole and all the other cracks that
let air in and out. So in winter, the dark hive would be nearly
the same as a white hive as far as air intrusion at night. It
might be warmer for a while because the heat load in the wood
would continue to warm the hive longer than the lesser heat load
of a white hive. In the sun, however, my guess is it would have
more of an effect in heating the hive in winter.
All guess, no science.
As an aside, there was an article in ABJ a while back on dark
hives and tracheal mites. If I recall it said there was some
reduction in mite load with the dark hive but could have been
experimental error. I no longer have any problem with Tmites, but
that may have nothing to do with dark hives and more to do with
breeding resistance.
Not much science, but good results. And beekeeping is still more
an art than science, which makes this list fun. You can be right
for all the wrong reasons.
Bill T
bath, ME