Anodizing is part of an electrochemical manufacturing process that gives a lot of modern tech its soft finish, durability, and rich colours. It allows metals like Titanium and Alyour gadgetuminium to not only receive a layer of protection, but also an impressive colour that is not painted, but rather dyed into the material and then sealed in.
Though Apple were amongst the first manufacturers to use this process on a large scale to create the bodies of their products (e.g the iPod Nano and newer Macbook line). The method has been uptaken by other companies such as HTC who use it on the One S. Many other manufacturers are expected to use similar processes on phones being released later this year.
Check out Bill Hammock’s video (The Engineer Guy) to get a terrific in-depth demonstration and example of how the Anodizing process works, plus how devices get their colours. Some really interesting stuff.