The same solutions used to color Cast Iron can be used to blacken stainless steel.
You can't use the same tanks as you would for standard blueing solution, you have to use different tanks, ceramic is supposed to be best, ha, I can't afford ceramic tanks but an alternative is to find a couple old pocelain covered cast iron clawfoot bathtubs.
If you try to do this finish process in black iron blueing tanks the finish will end up being copper colored.