Cone 6: Eggplant is an opaque, gloss purple glaze. Three coats will create a solid purple finish. Thinner applications may result in the development of blue-gray coloring. Blue-gray colors may also develop where the glaze breaks over and around surface textures. Cone 10: Color changes to blue. TIP: A light blue can form on top of Eggplant where it pools; surface textures also encourage the glaze to break blue. It is beautiful used in combination with other glazes.