The manufacturing technique should be very flexible, to boot. We already knew that 3D Systems would be making conductive ink (with the help of Carnegie Mellon University and X5 Systems) to print working parts, like antennas. However, it will also print parts in a "full spectrum" of colors, including transparencies; there's a possibility that you'll get parts for your Project Ara phone in the exact hues you want. You'll still have to wait until 2015 to get a modular mobile device of your own, but you'll at least know how it came into being.