You don't really notice the green in everyday use. If you double check the pictures, the green of the "juice pack" is the same green as the iPhone's battery icon. No doubt some design artist thought that would be cute. Black would have been cuter.

Aesthetics aside, the Juice Pack is awesome. Good fit in the hand, not too hefty in the weight, and battery life forever.

My only gripe about the thing is that the supposed pass-through dock connector only passes through charging current. Very disappointing to have to take the iPhone out of the Juice Pack to sync the phone with the computer. What were they thinking?