Both Surgical Steel and Titanium are basically "silver colored" but are nowadays available in several different colors.
These jewellery comes in 4 different colours, they are not "colored" in the classic sense, it is made of Steel 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.