I can add a little to this post I think.
I'm not sure if the color affects the battery at all, but it sure affects the cabin temperature and the energy needed to keep the interior cool on a sunny day.

Try this test, go to ANY car dealer and ANY car model for sale on a sunny day. Pick a light colored and a dark colored car next to each other. Put your hand on each one. I was BLOWN AWAY by the difference in temperature on both cars by simply touching the roof of each. The lighter colors were just barely warm to the touch, while it was difficult to hold my hand on the same exact car with a dark color (TOO HOT).

I know this is BASIC KNOWLEDGE and not some scientific break through, but I can tell you that I never expected the difference to be as severe as I learned on that day.


Food for thought.
08FEH

Of course darker car gets hotter in the sun, I had silver and red car, red car was always about 10F hotter inside when both were sitting in the sun. And it's not about something breaking down either, it's about efficiency. Hotter car will take longer to cool it and battery itself will reach higher temperature faster under the same load if it starts at higher temperature, therefore it may use ICE more often to keep the battery within operating range. Running fan in the parked car makes no sense, the hottest air is on the top, right under the window, just where the fan intake is, I would imagine battery being low inside the trunk have one of the cooler places in the whole car. Only when you drive with AC on will running fan start making sense to keep the battery cool, but that's when it needs it the most.