Chuck
I had a set plated black zinc last winter and they have been on my Camaro since then. I had de vaned the A.I.R pump and blocked the tubes.
They look OK but are not correct. If one was concerned about that...and I am not..
I may take some original's to my plater to look at sometime.
As mentioned already, they may have been clear cad/zinc plated and died. My plater showed me some bolts done that way and dyed OD green.
NOS and original tubes are all over the place with color from very bronze to several shades of green of green-brown.