BLUESTONE BLUE FLAME 20X72X1.5 20" x 72" 1.5" Tread Bluestone Blue Flamed has a flamed finish and is a beautiful natural stone that is highly desirable. The flamed finish is a treatment achieved with high intensity heat to remove the natural clefts. Typically comes in a blue-gray color but it is also available in a variety of colors that includes more earthy tones.