Both Surgical Steel and Titanium are basically "silver colored" but are nowadays available in several different colors.
Zirconline® is gold colored jewelry, they are not "colored" in the classic sense, this item is made of Titanium that is covered with a thin plasma film (PVD coating). The thin film is very strong and does not fade. The technology has been used in the medical industry since the late 80's and is used, among other things, for pacemakers and orthopedic implants to provide an extra durable surface.
Zirconline® looks like real Gold, and is incredibly popular in our webshop.