Those born in October have two birthstones to choose from: opal and pink tourmaline. Opal is the traditional birthstone for October, while pink tourmaline is the modern birthstone. Opals can be almost any color, including red, yellow, white, and black, and they often display a "play-of-color" effect, which is a pattern of colored flashes distributed throughout the stone. The flashes can be blue, green, orange, or red, and individual stones may show none, some, or all of these colors at once. Pink tourmaline, on the other hand, can be found in almost every color, including pink, red, green, blue, violet, and black. Therefore, the color of the October birthstone depends on which stone you choose.