Color

There are several scales used for judging the color of a diamond, but the most common is an alphanumeric scale widely used in the US. The Gemological Institute of America grades diamond color from D (totally colorless, sometimes called “white”) to Z (yellow). A "colorless" diamond is graded as D, E, or F but the differences in each grade are small and usually only obvious to a trained expert, so the difference between an F diamond and a G diamond is very small.  The average color for engagement diamonds is G or H.

Experienced gemologists grade a diamond’s color by placing the diamond facedown on a white background. Gemologists look at the hue (the color tone of the body) of a diamond by comparing it against a set of standards that have been approved by the Gemological Institute of America. The gemologist then assigns a color letter grade to the stone and this is entered on the diamond’s certificate. Diamonds for jewelry usually fall in the G to J range.

In nature, diamonds range in color from white (colorless) through slightly yellow or brownish. There are some stones that have chemical impurities that tint the diamond a different color such as blue, green or pink. These are called fancy diamonds and are rare and costly.

Diamonds with D, E or F color are considered colorless; G, H, I and J colors are near colorless; K, L, and M colors are a faint yellow; N through R have a light yellow tint; S through Z are light yellow. The most valuable stone is a D color, which is perfectly colorless, but these are extremely rare and hence very valuable. The color of the stone can be affected by the mounting. A slightly colored stone can appear colorless when properly mounted. A yellow gold mounting also makes very slight colors almost impossible to detect.

Color alone does not make a diamond valuable. The other Cs (cut, clarity, carat) must also be considered. A D color diamond with a poor cut is not as valuable as an ideal cut G color of the same size.