With Midnight Blue I was looking for a darker blue, transitioning from the highly saturated Navy Blue to Black and Gunmetal Grey. While fading into dark I pulled out some of the blue too which should give it a tiny bit more of a coated or surface treated metal look than plastic. This looks really great in low light where the shaded parts start disappearing in the dark leaving just a few bright reflection points.
The print of the terminator T-800 is an almost perfect use case, an example of scary looking metal without having to give up entirely on color. And I think it looks a lot better than just printing this in black or grey.