Volt is machined from pure titanium. It features polished chamfered edges and a V shaped groove around the circumference. The V groove and the interior of the ring are anodised accordingly.
There are no dyes used, it is a purely optical effect. The colour is achieved thanks to an innate property of the element titanium. Titanium naturally forms an "oxide layer" on the surface when exposed to the air, this oxide layer acts as a protective barrier, giving the titanium it's complete resistance to corrosion.
When we anodise titanium, we are increasing the thickness of this natural oxide layer. The increased thickness alters the way photons of light reflect off the ring, producing its characteristic colour.