Color refers to the presence or absence of color in white diamonds. Acting as a prism, a diamond can divide light into a spectrum of colors and reflect this light as colorful flashes called fire. Just as when looking through colored glass, color in a diamond will act as a filter, and will diminish the spectrum of color emitted. The less color in a diamond, the more colorful the fire, and the better the color grade.

In the 1950s, GIA esstablished a color-grading system for diamonds. Because many of the color-grading systems that came before it used vaguely defined trade terms, GIA wanted its system to clarity the color-grade categories.

The GIA Color Scale begins with D(colorless) and continues through the alphabet to Z(light yellow). A diamond's color grade is based on the tone and saturation of its color, or its absence of color.

Each letter on the scale represents a narrow color range, not a specific point. And each master stone marks the highest point-or least amount of color-in that range. A diamond with slightly less color than the H master stone is considered G-color, one with slightly less color than the G master stone is considered F-color, and so on. Five diamonds graded G can have five very slightly different amounts of color, but they all must have less color than the H master stone, and more color than or an equal amount of color to the G. If a diamond has less color than an E master stone, it’s a D. This means there’s no need for a D master stone.

The levels of the GIA Color Scale can be divided into colorless, near-colorless, faint yellow, very light yellow, and light yellow ranges.

The D-E-F grades are considered colorless. D and E diamonds have virtually no color, and an F has a nearly undetectable amount of color that shows only in the face-down position. The differences between these grades are actually very slight. In face, they are almost indistinguishable in diamonds smaller than 0.25 ct. Diamonds in this color range are extremely rare and valuable.

The G-H-I-J grades are near-colorless. Diamonds with these grades look colorless face-up and nearly colorless face-down. They have slight traces of color that are not noticeable to untrained eyes when the stones are mounted. These diamonds are popular because they combine fairly high color with somewhat lower prices.

The K-L-M grades are faint yellow. Diamonds in this range show very faint yellow color face-up and face-down. When they are mounted, small stones look colorless, but large ones show a slight yellow tint.

N through R diamonds are considered very light yellow. They appear very light yellow face-up and face-down, even when they are mounted in jewelry.

S through Z diamonds are light yellow. They show substantial color face-up or face-down, loose or mounted. Once a diamond goes beyond the Z color range, it’s classified as Fancy Light yellow, which causes its price to rise. Sometimes, diamond rough with color in the X to Z range can be cut to achieve a fancy-color designation.

Each letter on the scale represents a narrow range of color, and each masterstone marks the least amount of color in that range.