Dichroic coating Aurora Borealis Cyan Dark Dark Red on thin glass COE 90. Aurora Borealis Cyan Dark Dark Red is a CBS premium dichroic coating. Aurora Borealis Cyan Dark Dark Red fires to a vairiety of red, orange and gold colors. This coating is offered on clear and black glass in a 4x4 inch square or a quarter sheet. There are approximately 66 square inches in a quarter sheet of glass. Please Note:  All photos on black glass.