Color refers to the natural tint inherent in white diamonds. In nature, most white diamonds have a slight tint of yellow or brown color. The closer to being “colorless” a diamond is, the rarer it is. The industry standard for grading color is to evaluate each stone against a master set and assign a letter grade from “D” (colorless) to “Z” (light yellow).
Tiffany only accepts diamonds in the “colorless” and “near colorless” range on a diamond color scale. Borderline diamond color classifications are automatically given the more conservative grade. Additionally, the Tiffany Gemological Laboratory will not accept stones exhibiting strong or excessive fluorescence, which, in natural lighting, can give diamonds a milky appearance.