Diamond color grading is a process used to evaluate the color of a diamond. It typically ranges from D (colorless) to Z (light yellow or brown). The grading is based on how much color is present in the diamond, with colorless diamonds being the most valuable. Grading is performed under controlled lighting conditions and involves comparing the diamond to a set of master stones. Factors such as hue, tone, and saturation are considered. This systematic approach helps buyers understand the quality and value of a diamond, ensuring informed purchasing decisions.