In this link, http://www.exploratorium.edu/snacks/colored_shadows/index.html, the second illustration is the shade of green that I saw.

Rap: "Was there one of those orange lights nearby?"

Yes, the street lamp is more orange than white. However, everywhere else I looked, the shadows it cast were black. Why only on the white car was it green?

The fence, Desert Dancer, was/is one of those nondescript gray metal ones, rounded, probably hollow.

The fact that the color was the exact shade of green that Becky linked to makes me sure that this is what is going on, but I still don't know how. There is no other light in the area..

Is it possible that the street lamp itself is prismatic? But again: why were the other shadows black?