Lots of multicolored gems! Either in the form of bicolors like tourmalines, or pleochroic gems like tanzanite and kornerupine, or color play stones like opal, or organic gems like ammolite, or (if this fit your idea) feldspars like labradorite and sunstone.
Don't forget about Parti Sapphires, there are some really cool Aussie partis that have awesome blues, yellows and greens!