The Nikon Df is an odd duck in the Nikon DSLR lineup. It's certainly a premium product, at the $2,999 kit price that Nikon is asking for, but it's definitely not a professionally-oriented camera. However, there's no denying that it's a pretty camera, the silver/black version even more so than the all-black. Hence, the all-black tester; our hosts were long since out of the silver version by the time I got around to trying the new camera.
That in itself is indicative that Nikon nailed the marketing for the Df. It's aimed at the traditional high-end camera buyer... though the D4-evolution sensor at this price point is impressive, Nikon has been fairly consistent since launch about de-emphasizing the specs of this camera and selling purely on emotional appeal. Hence, why silver has been the more popular colour since launch; it's the one that creates the most emotional appeal when lined up with the rest of Nikon's basic black cameras.