on a 64, the bulbs have a orange wire. Is this just a ground?

on a 64, the bulbs have a orange wire. Is this just a ground?
There's no orange in the tail light wiring, there's a brown (tail lights) a tan (fuel sender) the tail light bulbs ground to the socket, to the assembly, to the body.
The only orange is the dome light positive, which should branch off under the parcel shelf with the white negative switch wire.
hope that helps