This seems to be happening to many Z3 owners, so I would advise anyone reading this thread to test out their camera on the phone. This is probably a software related issue with the Z3--when shooting a plain white/gray/brown surface, a noticeable pink spot can be seen in the middle of the photos. This happens both in SUPERIOR AUTO and manual mode.
Sample shots:
Sony thread:
Pink spot with xperia z3 camera - Support forum
Reddit:
Sony Xperia Z3 owners: do you also have a pink spot in the pictures you take? : Android
Sample shots:



Sony thread:
Pink spot with xperia z3 camera - Support forum
Reddit:
Sony Xperia Z3 owners: do you also have a pink spot in the pictures you take? : Android