Gansai Tambi This watercolor set features 6 opal tones. The included colors are opal pink, opal copper, opal gold, opal green, opal blue, and opal violet. These iridescent colors make pale, pearly marks on white paper and strong metallic marks on dark paper. They can be used by themselves or with your favorite transparent watercolors. When added to regular transparent watercolors they will give a secondary color shift. For example: If you add opal blue to a yellow watercolor, it will not make green. Instead you will have a yellow base with a secondary blue color you see when you move the paper around.