Enamel is the outer covering of the tooth. It is composed of minerals, primarily hydroxyapatite (a naturally occurring mineral form of calcium apatite). Enamel is the hardest tissue in the human body. It covers the Crown of the tooth.
Enamel is translucent, so you can see light through it. The color of your teeth is determined by the Dentin beneath the Enamel, not by the Enamel itself.