Diamond color is the main criteria of grading. The color grading system actually refers to the degree to which the diamond is colorless. Diamonds can be found in many colors, yet white-colored or colorless diamonds remain the most popular.
Diamonds are graded on a color scale, which ranges from D (colorless) to Z. Different ranges of the scale look well with different materials and colors. To over-simplify: the best white-colored diamonds (D-J) look stunning set in white gold or platinum whereas warmer colored diamonds (K-Z) are particularly desirable when set in yellow gold. Truly colorless stones (graded D) are treasured for their rarity and are amongst the most expensive.
Color differences are usually very small, making it very difficult to distinguish an E and an F, for example. Therefore, colors are graded by trained professionals under controlled lighting conditions and are compared to a master set for accuracy.
Diamonds can exist in a number of shades such as: green, blue, red, orange, pink, yellow, etc. Red is the rarest of the natural colors and is therefore the most expensive. Diamonds that exhibit these natural colors are known as “colored fancies”.