Nice.

Depends on what it's made of tungsten for example can do all sorts of colours depending how it's heat treated

Coloring is likely a side effect of heat treatment, titanium dioxide film or both.

Can be from tempering, but it's usually hard to get the color that consistent. It could also be anodized or acid treated. There's a lot of different ways to change the color of steel.

What part of anything on this post points to this being a functional sword? Pretty obviously meant to be an art piece.