The birthstones for October are opal and tourmaline. Opal is the traditional birthstone for October, while tourmaline is the modern one. Opals are known for their "play-of-color," or ability to shift hues, and come in many different colors. Tourmaline, on the other hand, comes in a rainbow of colors, including pink, red, green, blue, violet, and black. Both opal and tourmaline are multi-colored, and their array of colors helps October birthstone jewelry stand out.