Birthstone: Opal & Tourmaline - The Rainbow Stone(s). Opal & Tourmaline both have the unique properties to show a spectrum of colors in one gem. Tourmaline can be solid, or a literal rainbow of color; from green, pink and gold, to red and yellow. Opal is a conflagration of colored flecks, a riot of color, and the name is derived from Greek, the ancient term Opallus, meaning "to see a change (of color)." Both of October’s colorful stones symbolize peace, hope and symbol for meditated change.