Naturally colored diamonds, or "fancies," are very rare. The color results from imperfections in the diamond's structure or from trace elements within the stone. Nitrogen, for example, turns diamonds yellow, while boron makes them blue. Because of their scarcity, colored diamonds are more expensive. According to Henri Barguirdjian, president of Graff America, "a fine-quality one-carat pink diamond may cost 20 times that of a comparable white diamond." Colors like red, green, and dark blue are incredibly hard to find, followed by pink, lavender, and lighter blues and greens. However, yellow and brown are more common.