Sonny Dockson, at his blog writes:

Up to this point, it has widely been thought that the iPhone 5S will only come in 3 colors: Gold, Slate, and white with silver trim. According to a new images we’ve obtained, however, it appears the iPhone 5S may also come in a 4th color – a grey or graphite color with a black trim. You can check out samples in the below gallery! Richard Padilla, at Macrumors writes: Sonny Dickson has posted new photos showing alleged parts from a "graphite" colored iPhone 5S, which could be a fourth color choice for the phone in addition to the expected black and white choices, as well as the all but confirmed "champagne" color option. The photos show the device from numerous angles with the back, front, and screen housing assembled, and also show it next to the champagne iPhone 5S and iPhone 5S screen assembly. These all seem quite plausible.