That's not a Galaxy S. Look close. The metal ring (the one that go around the phone) is in a different position for both colors. There's also a camera button on the side. Lastly there seems to be a metal ring around the home button. Reflective as the galaxy S plastic is, it's not going to turn silver.
That's probably the media player version of the Galaxy S. Or as they say, a completely new phone called Galaxy U, but that would be strange considering there is almost no pre-release coverage of the device.