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.