From D (colorless) to Z (faint yellow). Precision color analysis for every diamond.
Diamond color grading assesses the absence of color in a diamond. The less color a diamond has, the higher its color grade and generally the greater its value. BGI follows the international D-to-Z color grading scale, where D represents completely colorless and Z indicates a noticeable yellow or brown tint.
What makes BGI's color grading distinctive within the 6C system is our use of advanced colorimeter technology combined with traditional gemological expertise. This dual approach ensures objective, reproducible results that stand up to the highest scientific scrutiny.
BGI gemologists grade diamond color using calibrated colorimeters and spectrophotometers under standardized D65 daylight lighting. Each diamond is placed table-down on a neutral white surface, and the color is observed through the pavilion. Multiple readings are taken and averaged to eliminate any variance.
The colorimeter provides quantitative spectral data that is cross-referenced against master stone sets. This instrument-based approach reduces human subjectivity and ensures consistency across all BGI certificates worldwide.
Colorless diamonds (D-F grade) are the rarest and most valuable. Near-colorless diamonds (G-J) offer excellent value and appear colorless to most untrained observers once set in jewelry. Faint-to-light yellow diamonds (K-Z) can be an attractive option for budget-conscious buyers or those seeking warm-toned vintage aesthetics.
Fancy color diamonds (yellow, pink, blue, green) are graded on a completely separate scale and are not part of the D-Z system. BGI offers specialized fancy color grading as part of our comprehensive certification services.
| Grade Range | Category | Description |
|---|---|---|
| D – E | Colorless | Absolutely colorless. The highest grade, extremely rare. |
| F – G | Near Colorless | Color difficult to detect except by trained gemologists. |
| H – I – J | Faint Color | Slight warmth visible when compared to higher grades. |
| K – M | Very Light | Noticeable yellow or brown tint. |
| N – Z | Light | Visible color throughout. Often used for industrial or budget jewelry. |
Last Updated: June 2026 · BGI 6C Diamond Standards™