I've shot quite a few test pictures in various light conditions and have seen no purple effect in any of them. I have the Black phone as well. I'm actually quite impressed with the camera, although it's never the reason I buy the phone. I always consider cameras on phones to be more of a toy, and prefer to use my dedicated photography equipment for shoots.
Having said that, as a point and shoot camera, the iPhone 5 does a very good job indeed.