I recently bought a Cyprus Green and had that feeling too. The Plum feels "normal" but the CG was definitely more rubbery than usual. It also felt thicker. Like the very early bands.
edit: I just pulled Grapefruit to wear today for the daily show & tell. And I can most certainly say that the feeling is not the same. Grapefruit feels softer and more velvet-y. So I guess
@FenC 's comment about darker bands being harder and shinier, definitely has something.
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edit: so same impressions as already posted by
@myrtlebee and others 😊