My second theory is, I believe, far more likely to be correct. The white Star Destroyer is closer to our mental image of the classic Star Destroyer than the real thing. To capture the classic look, the creators of Rogue One have slightly altered the original look of the Star Destroyer paradoxically to make the aesthetic feel more like a throwback. The first, frankly, is a trifle: The Star Destroyer is white, instead of the murky grey of the Star Destroyers in the original trilogy, because white was largely used by the costume designers and scenic artists of the 1970's science-fiction cinema. Of course you've already watched the Rogue One: A Star Wars Story trailer, so let's assume you care about the roughly two minutes of footage enough to speculate on the big question at its heart: why are the Star Destroyers so starchy white?
