I suppose it is the spec then, but the "nozzles" (?) of the gun (where stuff comes out) are just grey, the concept adds a bit of detail to it with some extra lines ringing around them (in addition to highlights from the metal).
You have a point about the lighting being blue, not the texture too. All the metal parts hace a sort of cool hue to them, which could indeed be light interacting with the metal components, while keeping the grip and non-metal components a more matte grey. (Such as multi-layered materials like a car or coated metals.) In either case, I
would, add a hint of gray-blue to it, it suits me better, personally. Completely up to you though.
On another note, looking at the concept more, the multiple displays it has slightly change in greyscale. The circular disk things, near the front (with the "nozzles") are the same hue and saturation as the rest in the main shot, but in the lower left front view, they are lighter.
Lastly, it is a concept. One's idea. I'd like to see this with a bit of your own touch to it, nothing heavy duty, but you know, something that makes it even cooler, one of those "you know what it's missing? This." kind of touches. Maybe?