it's s35vn steel right? that's too stainless to actually patina. I'm not sure gun bluing would work on stainless at all, and with the finish of the knife. even cold bluing I don't see it workin. even if the cold bluing stuck, it wouldn't last.
cerakoting would work....but doesn't hold up well. other pvd and dlc type finishes would work also. would require prep work and such, not something ya can do at home that i know of......