Have noticed a metalic like sheen in faces in Red footage from the beginning. I wanted tosee this film to see if it was no longer evident. I've noticed it getting less and less over the years. I aim to see the Amazing Spider Man to confirm. I originally thought this might be related to color toning before, maybe to do with debayering on large areas of similar color flattening out.
Go watch Pirates of the Caribbean: On Dangerous Tides on Blu-ray -- all shot on Red, color-corrected by Stefan Sonnenfeld and the gang at CO3 in Santa Monica. Beautiful-looking film, very atmospheric, runs the gamut (no pun intended) from saturated to very bleak. Sharp as a pin, great exposures. Debayering has no effect like you describe, not in my experience.