If the screen on the 6 is as easy to swap as the screen on the 5, you could buy the Gold 6 and wait until they start selling the screens at ifixit or ebay. Then buy a black 6 screen and swap it out.
Sure, it's an extra $50 to $100 for the screen, but you'd have a unique iPhone6 and you could probably sell the original screen for a few bucks.