[Question] How was this "dark chrome" look achieved?

I know nothing about wheel modding, so I'm sorry if this is frowned upon. But a few months ago I was looking for a new car, and came across a used Mazda 6 at a dealership that had wheels that looked like they were a dark chrome color.

How is this done? Are the wheels painted somehow (maybe powder-coated)? Is this something you could do or have done to your wheels, or would you have to buy them like that?