I did a run-through of my figures a few days ago and ran across a couple that had started to go green, and perhaps not surprisingly, they were both from 2002 and 2003: the aforementioned Saga '03 Snowtrooper, whose kama and helmet, like Chewie's, had turned lime green, and the 2002 electronic R2-D2 (the one that came with the Kouhuns), whose legs (but not body or feet) had turned the same green color. I was able to get the R2 green gunk off with Goo Gone, but the Snowtrooper has not been so lucky.
I keep my figures in Plano tackle boxes and out of light, and those were the only two figures that had shown any serious deterioration in white portions. The 2003 McQuarrie Stormtrooper was yellowing slightly, but not terribly bad, and definitely wasn't turning green.
