Peter W.. Rowe, wrote:

You can come closer to copper color using solders that aren't intended for
jewelry. Some of them (usually called brazing alloys, rather than silver
solders, because they're usually aimed at industry which calls the process
brazing rather than soldering (a word *they* reserve for when you use things
like tin/lead solders...) are more brass colored than silver colored, and they
will not have so much of a color difference. But they're usually still not a
true copper color.

Yes, it is called phos-copper rod, available at many welding shops.
Sculptors loved it in the 50s and 60s when direct metal sculpture
was all the rage. Makes a nice copper colored joint.