TREASURES OF THE SEA SERIES. Blue Paua Shell earrings. Small Approx. 3/8 Diameter. Paua, a species of abalone is the most colorful shell in the world, other abalone have some color, but not the brilliance of Paua. The color in the paua shell changes when viewed at different angles. This iridescence, similar to that of Mother of Pearl shell, but far more brilliant, is what makes paua shell so interesting as a gem material for use in jewelry. These brilliant colors are from light refracting within the crystal layers of the shell.