Because the copper wire is plated with a layer of silver.
Because the copper wire is plated with a layer of silver, it is silver. The electrical conductivity of silver is higher than that of other metallic materials. Many solar panels now feature silver-plated wires.
Silver-plated copper wire is relatively soft and has good electrical conductivity. Compared with bare copper wire, it has stronger corrosion resistance and oxidation resistance, which can greatly extend the life of low-current cables. Silver plated copper wire is easy to use but expensive. Of course it is coated, and it is coated with silver depending on the physical and chemical properties of the coating.