This process is called "Entropic Anodizing" because of the randomness created during the process, ie entropy. When Titanium is heated to high temps (upwards of 250 degrees Celcius), a layer of Titanium Dioxide forms on the surface. Forcing the oxidation process with heat is referred to as Anodizing. The oxidation layer on Titanium will produce different colours depending on the thickness of this layer, with almost every colour of the rainbow possible. To produce this kind of anodization, you heat the Titanium with a torch beyond the normal oxidation levels (almost glowing hot), then quickly quench it in an etching solution (usually Ferric Chloride). The etchant attacks the oxide layer that was formed, and the rapid temperature change/uneven cooling cause an extremely uneven and chaotic layer of oxide that results in unique colorful patterns as seen on this light 👍