It’s always a good idea to think about your state of alertness concerning your eyes and mind. Mistakes are easily made after hours of grading or mental effort of any kind. Make sure the color grading tray is a non-fluorescent type such as the plastic tray GIA sells. The bright white fluorescent paper trays that many dealers give away as promotion will detract yellow and not give you an accurate impression of color. The paper color grading tray included with this course is non-fluorescent. Lay the diamond in question table down inside the tray looking directly into the pavilion in a perpendicular direction. Practice without a master stone first and then lay the comparison next to the stone in question to see how close your estimate is.