Looks like this one is 240V with a 120V PC, or at least it used to be when it was MV? I see the white wire and two hots. Around here the utility company's lights were all 240V with 120V PCs from about 1965 until around 1989. When going HPS in the late 80s and early 90s, they simply snipped one of the hots where it connected to the triplex and pulled the snipped hot wire out of the arm, leaving just one black and one white for the 120V HPS fixture to connect to.

Hmm I'm not sure,I would have to go take a closer look at it,I figured the bluish wire was a faded green ground wire.

Ah now that you mention it, it looks like that wire goes around to the side of the fixture rather than inside it so it must be a ground... Though seems like a ground connection would normally be made inside?

On the Westy brackets they have a grounding lug on the outside,the fixtures come equipped with approximately 24" long power leads.

Where can you get wires that can be exposed to the sun/UV? I know about UF cable, but the individual wires inside the UF jacket cannot be left exposed long-term.

The best bet would be an electrical supply house,I don't think Home Depot or Lowes has anything, RWU90 stranded single conductor cable in black is sun resistant.