They have announced a simple process where you can send in your iPhone 3G S and have the back cover dyed to a different color. But the fun does not stop there.
You can have them change the normally chrome bezel, the home button, your headphones, and the SIM-Card holder. You do have to send the phone to them (if you are in the US) to get these exciting new colors added.
You might want to do this while you are waiting for AT&T to activate MSS and tethering or while you wait for a jailbreak from the devteam.
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The usual range of solid and metallic colors are available, and you can have your earphones dyed to match too. The basic process changes just the back-plate of the phone, but you can also customize the normally-chrome bezel, the home button and the SIM holder.
Pricing starts at $150 for the back, then add $20 each for the bezel frame and button, or $15 each for the SIM holder and earbuds. Currently there's only the option to send in your own iPhone 3GS (in the US); ColorWare aren't offering the smartphone themselves at this stage.