Diamonds are not all truly colorless, but it's the colorless, often called white. The Gemological Institute of America (GIA) has devised a set of guidelines to grade diamonds by color (D-to-Z). Diamonds in the D-to-Z range usually decrease in value as the color becomes more obvious. Just the opposite happens with fancy-colored diamonds - value usually increases as the color deepens.

Grading fancy color diamonds is a complex process. The color is assessed in three ways:

	Hue (the aspect that gives the color its name - like red, orange, or blue) There are 27 hues of color grading diamonds. Each of the 27 hues represents a range of colors. The 27-hues consist of basic colors like red, orange, blue and mixed colors like orange red, green blue, and greenish yellow, which is the predominant hue.
	Tone (the lightness to darkness of the color) Zero tone is white and 100 is black
	Saturation (the strength or purity of the color) There are 9 different categories used in describing the combined affect of tone to grade the saturation and to identify the ranges of color appearance. They are:

Usually, the deeper the color, the rarer and more expensive the diamond will be. For example, a fancy light pink diamond costs less than a fancy vivid pink diamond of equal size, shape and clarity.

The predominant hue is always expressed as a noun, such as "pink." Any secondary colors will precede the primary hue and are usually expressed with an "ish" at the end, such as purplish pink. This means that the dominant color is pink with some hints of purple throughout.

If the grade is stated as two nouns--like "brown pink," it means that the two colors are virtually even throughout the stone.