Sorry to bump this old thread, but I just wanted to say thanks.
I've been searching for ever for some advice on the exact same situation with my loin which has been dry curing for 15 days, and being turned every other day. It was cured in dry mix of 3% salt (I did 2% and 2.5% before, and I felt both needed to be more salty), 0.25% Prague #1 and I forget how much brown sugar.
It's my first loin cure, having done a couple of bellies before, some areas of the middle and bottom (the exact same as OP) have turned that same colour, so I was looking to ensure I hadn't over cured or not turned enough or that it has just gone rotten. There is no bad smell whatsoever. I smoked it today, and it looks the same colour, but your reply regarding the myoglobin and the process by which the muscle changes colour put my mind at ease.
