Both Surgical Steel and Titanium are basically "silver colored" but are nowadays available in several different colors.
Blackline® is black jewelry, they are not "colored" black in the classic sense, it is 316L Steel or 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 since the late 80's and is used, among other things, for orthopedic implants to provide an extra durable surface.
Blackline® is glossy black and a delight to the eye, they are incredibly beautiful as they are but also really cool if you combine with other colors.
What is PVD Coating? (Physical Vapour Deposition)
The jewelry is coated in a heated chamber under high vacuum. Electric voltage applied will form a plasma in the chamber andthe introduction of various gases produces an ion bombardment. This bombardment atomizes the cathode material (titanium) into tiny substances which are deposited on the jewelry. The result is a hardened layer, which is biocompatible. It can be autoclaved.