The Enameler introduces color either by using coloured glass or by adding pigments into the glass ahead of firing. Once the glass melts and flows, it cools into a tough, smooth coating about the substrate. Encapsulating this Beautiful dial is actually a 38mm 18K yellow gold case with 10.7mm thickness, https://www.watchesworld.com/exploring-the-aesthetics-of-dial-design-and-decoration/