Summary: How Different Labs Grade Color
The gia and ags have different color grading scales of which to determine the color of a diamond.
While GIA is the leading and most respected of the grading laboratories, there are other highly respectable gemological laboratories that grade diamonds for color as well. The primary one and most respected of these is AGS, American Gemological Society. EGL, European Gemological Society, and IGI, International Gemological Institute, also have color grading scales, which are similar in nomenclature to GIA's. However, neither EGL nor IGI are as strict or stringent in their color grading as GIA or AGS, thus resulting in inflated grades over what you would get from either GIA or AGS.
AGS uses a color grading scale that is comparable to the GIA color scale, but it is not as comprehensive, and lists its grades using numbers as opposed to GIA's letters. The AGS color grade scale runs from 0 to 10, with 0 corresponding to the GIA's "D" and 10 corresponding to the GIA's "V-Z". The AGS grading scale, in comparison to GIA's runs as follows:
| AGS | GIA |
| 0 | D |
| 1 | E |
| 2 | F |
| 3 | G |
| 4 | H |
| 5 | I, J |
| 6 | K, L |
| 7 | M, N |
| 8 | O, P, Q |
| 9 | R-U |
| 10 | V-Z |
If you have ideas on how we can make our site better, or if you've come across an error, we'd love to know.