There are as many coatings as there are steels.
Kershaw uses alot of Tungsten DLC (Diamond Like Coating) in black . Similar coatings to a Tungsten DLC, is Crystalline Diamond, Titankote C10, Balzers Balinit Diamond, Titankote DLC, etc
Benchmade uses a proprietary coating called BT2 on some items
Some blades like 1095 are just powder coated, or coated with a phosphate black or black oxide
Kershaw has used a rainbow Titanium Oxide coating similiar to the rainbow Titanium coating found on Sig Sauer’s P238 Rainbow.
Overall, my gut feeling is that you will see coatings similar to, or different flavors of a TiN coating which is Titanium Nitride. By adding or removing different properties for hardness, lubricity, and aesthetics you can be all over the place.
Also some manufacturers are Cerakoting, and Duracoating blades, which is basically a hard paint with epoxies and ceramics in them.
