This is a sample titanium plate that has been anodized. Anodizing is actually a clear oxide layer built up by the application of electricity in a conductive bath. The oxide layer is extremely thin (on the order of a few angstroms), and its thickness dictates what color we see. The colors are the result of lightwave interference, the same principle that happens in a soap bubble or an oil slick on a wet parking lot. As you see, there are no true reds, blacks, or pure greens possible. Although it is an extremely hard surface, it is so thin that it nets out being only about as hard as glass. This is why anodizing is normally done down in grooves and not offered on an outer surface