Industrial design cannot be protected, but trade dress can. Trade dress protection is available when a particular, arbitrary and non-functional, design becomes distinctive of a product. For these aspects of design to be protected, it must actually be distinctive of the product (i.e. you can't just claim a mark on the gray/yellow combination, but you have to show, usually through surveys, that the market identifies that design with your product).
Industrial design usually won't qualify because it's functional. The color comes from the use of aluminum, aluminum is used for its structural properties, particular colors have more aesthetic value in the market, etc. Trade dress has to be more specific, not functional, and arbitrary.
A classic example is pink for Owens-Corning insulation. It's a totally arbitrary color choice for a product where aesthetics doesn't factor into buyers' choices, and had become strongly associated in the public with Owens-Corning's brand. If there was a functional reason for the pink color, or it was a situation where people would prefer a certain color for aesthetic reasons, the design choice wouldn't have been eligible for protection.