The GIA Gem Trade Laboratory (GIA GTL) presents the system it uses to color grade faceted colored diamonds, and the information on which it is based. This system involves a trained grader establishing the characteristic color in a standardized illumination and viewing environment, using various reference materials for color comparison. Here, the Munsell color system is used to illustrate the relationships between the different color terms used. GIA GTL "Fancy grade" nomenclature for colored diamonds has been expanded to better address all colors. This color terminology will soon be incorporated into a new GIA GTL colored diamond report.