Why not get a pink case for the green Nano? I've seen pink and green shown together.
Apple has been playing "color games" with various iPods for awhile now. I agree that they do this to boost sales, but nobody is forced to run out and buy the new color. I can understand why people would want to upgrade when a new generation comes out and the new features are desireable. However, even then, you have to ask yourself, "Is it really necessary to replace my perfectly serviceable iPod with a new one"?
Having the latest "style" has been part of the iPod cachet, something I have trouble understanding because I'm not in that demographic. This applies to cell phones too. My daughter pointed out to me all of the Verizon cell phones on the show Gossip Girl, a program sponsor. I told her how many years ago, cigarette companies advertised on TV and showed people smoking on shows -- to get you hooked. In my mind, what Verizon is doing is almost the same.