Well, I know the blue is definitely possible, as it's just a process with heat and oil... If it's steel, a brownish color should be easy as well, cuz rust. The trouble would be figuring out how to modify the rusting process to change the hue a bit, if you wanted to. It could then be sealed afterwards likely to prevent future corrosion.
If you want to go the rusty way then it would be better to start off with Cor-Ten steel and once the oxidation is what you want, you can oil it. I've had 2 sheets of Cor-Ten in my shop for years but haven't used them yet. Maybe I should. ;)
Might be interesting to see what colors you might get with the rust effect included.