As it happens I have 2 pairs of identical bike shoes - one white pair, one black pair. I don't notice any difference in foot temperature.
Black socks and white shoes is a legit combination - I've seen pro teams do it recently, so must be allowed.
What I'm now wondering is could I mix and match my black and white shoes? White on right, black on left? Perhaps with contrasting socks?
I definitely don't wear dark coloured jerseys in really hot weather. I think that would make a significant difference due to the relatively large surface area.