How to Judge Diamond Color
If you ask someone to evaluate a diamond’s color, and the person holds the diamond ring up to a light, stares at it a few seconds, and seriously tells you, “It has good color,” you’ve gone to the wrong person.
First, there’s no such thing as “good color.” Color is graded by letters (from D to Z, see Figure 1 below), and you are in search of a letter, not a non-specific term that may mean one thing to one person and a totally different thing to another. Expect a letter as your answer, or at least a range of letters.
Figure 1: GIA Diamond Color Grading Scale
Second, diamond color is not evaluated by simply holding the diamond ring to a light. This would require both perfect eyesight and perfect memory of the shades of diamond color. The diamond should be compared to the diamonds in a master set, where diamonds of varying colors have already been properly labeled. Evaluations against master sets should be accurate within one grade, depending on several factors, including the inspector’s ability, intensity of the light in the room, and the master set accuracy and quality (e.g. cubic zirconium master sets deteriorate over time).
Third, ring settings can obscure the true diamond color and influence the observer’s opinion. A proper diamond color evaluation should separate the diamond from the setting.
Fourth, if available, an expert will use a colorimeter. It can work on loose diamonds and set diamonds, so if the inspector has a colorimeter, you don’t need to worry about the diamond ring’s setting obscuring the actual diamond color. Colorimeters are accurate to within half a color grade.
Quick Judgment Method
If you are not is search of a precise evaluation but simply want a rough estimate of a diamond’s color, you may be in luck. Most people are simply looking for a diamond that appears to be “colorless” (D, E or F) or “near colorless” (G through J). Fold a clean, white business card in half and place the loose diamond in the fold. If you detect any yellow, the diamond is at best a K, a “faint yellow” grade, and possibly quite lower. If you don’t detect any hints of yellow, the diamond color is probably “colorless” or “near colorless,” a grade of J or above.