Hair color is generally determined by genes, such as black, golden yellow, brown and red. When people get old, their hair usually turns silvery white. Due to different races and regions, hair is black, golden, reddish brown, reddish brown, yellow, gray, and even green and red. Scientific research has proved that the color of hair is related to the difference of metal elements contained in hair. Black hair contains equal amounts of copper, iron and melanin. When the content of nickel increases, it will turn gray. Blonde hair contains titanium, reddish-brown hair contains molybdenum, reddish-brown hair contains cobalt besides copper and iron, and green hair contains too much copper. In some African countries, some children have red hair, which is caused by the serious shortage of protein.