Hi Chick,
Your hinge assembly looks more light gray than mine. Is yours oiled or dry? Mine is oiled and it turned (over time) from that gray like yours to a darker gray in the photo, which matches the hue of the spring on my car when viewed with the eye. The camera shows otherwise and that is likely due to the round shape of the spring reflecting the flashes light in a diverging pattern whereby the flatter shapes of the hinge reflect it back more to the lens (astrophotography is my passion so I'm familiar with light behavior)
If you ever parkerize a firearm (it is the same as phosphating) they too tend to darken over time when oiled. It is likely the oil causing that reaction. Thanks for the reply!
Mike