All of my steel end caps for the cocking tube, Triggers, Mag Release Arms, and Selectors were painted from the factory in either blue/gray or black depending on the year. I think the unpainted trigger, Mag Release Arm, Selector Lever are PTR features. I do have a 91 that was refinished by T. Dyer and he left all the mag release parts (including the paddle release) as bare phosphate; looks really nice like that.
Parkerized or Phosphate Finished:
1. Flashhider
2. Stock and forearm pins
3. Charging Handle
4. Rear Sight
5. Mag release Button - Mag Catch on the left side is painted
6. Pistol Grip Screw
7. Pin Retainers on the Stock
Best,
TC