Color
Color in Diamond grading actually refers to subtle differences in the body color or hue. The Diamond color scale begins at "D" (colorless) and goes to "Z" (fancy intense yellow) Although Diamonds occur naturally in a variety of colors, the average person thinks of Diamonds as white or colorless.

Actual colorless Diamonds (D - G) are quite expensive and for most people are cost-prohibitive. Diamonds that are near colorless (H - L) often appear colorless when mounted in jewelry and the average consumer will not detect any color, although many consumers may begin to see a subtle presence of color around "J".

                                        A representation of color, ranging from D to Z

 
At the cusp of the color scale are "L - M", since most consumers notice color in this range. Lower than "M" is very easy for consumers to see color.

COLOR is the most important factor in grading Colored Gemstones, and encompasses the three components of color: hue, tone, and saturation (intensity).
 

Extra Fine
Color should be the top known color for its variety. Color should be evenly distributed (no zoning) vividly saturated and of optimal tone (light to dark) for its variety.
 
Fine
Color is still highly desirable with slight deviations from Extra Fine. Possible deviations could be minor extinction (area where color darkens), slightly lighter or darker tone, and strong saturation.
 
Good
Color should still be desirable but farther from ideal. Possibly more extinction, lighter or darker tones, slight zoning and moderate strong saturation.
 
Fair
Color should still be desirable but farther from ideal. Possibly more extinction, lighter or darker tones, moderate zoning, and some grayish or brownish saturation may occur.
 
Commercial
Undesirable color due to wide variations from ideal. Extinction, heavy zoning, and grayish or brownish saturation are possible
 

Like the rest of the Four Cs, color's influence on value is directly related to its rarity.

Read about other THREE of the Four Cs (Carat, Clarity & Cut), and you will learn how color plays an important role in Diamond and Colored Gemstone certification