Has Samsung started using a new camera module? Pics taken indoor by the replacement phone look darker but this is just my subjective impression.
Both phones were originally manufactured in April 2014, according to the stickers in the battery compartment.
I got a CLN replacement yesterday due to a defective display. It has a blue sticker "NB 05/14" meaning it was refurbished in May 2014. When I compared the replacement with my old phone, I noticed that a camera lens on my old phone is bright purple under a fluorescent room light while the one on the replacement phone is very dark purple.