Color Grading Position (7.23)
Many dealers and gemologists insist that several grading positions (color viewing directions) are imperative. On a round brilliant, the color concentration has a tendency to lie near the culet of the diamond. In elongated fancy shapes, the color has a tendency to favor the ends of the shape. Also you will often notice that elongated fancy shapes will actually face-up darker in yellow tint than when looking through the pavilion. Generally the opposite holds true for rounds.
The first viewing position should be parallel to the girdle plane. If using masters, make sure these are in identical positions to the stone in question. The second viewing position should be perpendicular to the pavilion -- your line of vision meeting the pavilion surface at a right angle.
These two viewing positions should suffice in giving you an accurate color grade, but if you are still unsure, go on to additional viewing positions.
