IMHO painting cypress provides the keeping with better appearance, but doesn't do anything for the bees. I have both pine and cypress and only used deck sealant. Yes, they're getting a little dark, but all still solid after a near a decade.

Plywood is another story. Without a finish, kiss it goodbye.

Paint or no paint, sheet metal on top is the only thing that lasted for me.

I also doubt the color makes any meaningful difference with hive temperature. They'll fan if its hot and cluster if not.

For me its about advertising. Everyone will know what bright white boxes are. Not many will see natural wood and less will know what they are.