It is interesting that both opal and tourmaline are associated with many colors. In the instance of opal there are many colors within one stone. In the instance of tourmaline there are many stones—each with its own color. Of course, to complicate matters, there are tourmaline gems with multiple colors—lots and lots of colors—all within one stone, just presented differently to the eye than opal.
No wonder the most often-used nickname for tourmaline is The Rainbow Gem. Tourmaline comes in so many colors and so many shades of each color that it is a favorite of collectors. Many serious gem collectors have separate tourmaline collections within their overall collection.