Both Surgical Steel and Titanium are basically "silver colored" but are nowadays available in several different colors.
Steel Blackline® is black jewelry, not "dyed" black in the classic sense, it is 316L Steel 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 80s and is used, among other things, for implants to provide an extra durable surface.
Titan Blackline® is black jewelry in Titanium, not "dyed" black in the classic sense, the black color is created through an electrolytic anodizing process, not by applying an additional coating layer, such as PVD coating. This means that the black appearance does not come from a separate metal or material coating, but from a treatment of the titanium surface itself.
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.