The term "red copper" seems to be a quirky Chinese descriptor for copper in general. There are Chinese-made AC connectors, AC outlets, and binding posts that feature copper plated brass or phosphor bronze base metals, of which I have no interest in trying. In the case of some EIZZ and CMC connectors, some are clearly indicated as copper plated brass, but the design of the CMC CMC-585-CU-R binding post indicates a pure copper base metal with copper plating. Whether or not it is actually plated with copper, perhaps for the way it may look for example is unknown to me. Maybe it's a cultural thing not use the terms "bare" or "unplated", or maybe there is another explanation involved.
Another issue is a plating called rose gold, which is a multi-metal alloy plating known for use as a jewelry plating, which is sometimes called red copper plating via incorrect information from Chinese sellers.
