The ones shown in our Step by Step Guide How to Turn Bowling Balls into Yard Art and pictured in Wildflower Magazine Winter 2009, vol. 26, no. 2, pp. 30-31 uses iridescent flat floral marbles. The one that was created by Anne Linville seems to have blue (with some iridescence) flat floral marbles. If you were thinking of making one of these yard art bowling balls, I would imagine the color of the yard ball is limited only by the variety of the colors available in the floral marbles and your imagination.