My '97 Excella from "Cronology of Painting My Excella" fame has a factory painted white roof and yes, white absorbs less of the solar energy making it cooler.
On this thread I've read a lot about Plasticoat being the only clearcoat for aluminum. I may have an alternative. Last winter I had a brainstorm and invented the item shown below. To finish the aluminum components, I first did an alumiprep wash, then did a CLEAR alodine conversion coat (available from Aircraft Spruce, Inc.), then I painted it with clear Imron. Most people do not know that Imron starts out as a clear base then pigments are added to it to achieve the desired color. I used the clear base with no pigments. So far, the Imron is doing great, and it has a very near match to Airsteam clearcoat. Some people may not know it, but Imron is one of the few products which retains it's color over a long life with almost no yellowing. Where other linear urethanes yellow over time, Imron does not.
Durability? Time will tell, but it's doing fine so far.