I've pulled this example from the Literature folder, because I'm not sure that it's really a valid example:
In David Eddings' The Belgariad, Polgara's eyes are one of the few reliable indicators of her mood, flashing "a steely grey" when she's angry, and softening to blue when she's not.
I've read the books and it's not described as an unnatural color change from one color to a different one; it's that thing that can appear to happen to many people with blue eyes when they're angry. (I'm also going to ask in Is This An Example? in the forums)