Most diamonds suitable for gem use have trace elements of nitrogen that causes some level of yellow tint. The diamond industry uses a color grading system developed by the Gemological Institute of America (GIA) that ranges from D (completely colorless) to Z (fancy yellow color). Each letter grade corresponds to a small range of color and the color grade of a diamond is determined by comparing it to a set of master stones whose color grade has been determined by a grading laboratory like the GIA.

The top three color-grades D, E and F are considered Colorless. Color-grades G, H, I, and J are known as the Near Colorless and color grades K, L and M are labeled Faint Yellow. It is important to have the color grade designated by one of the top diamond grading laboratories such as the GIA (Gemological Institute of America) or AGS (American Gem Society). Color grades on other documentation can be exaggerated and not accurate relative to industry standards.

The bigger the diamond, the more obvious its color will be, just as a carafe of wine shows more color than a glassful. Some shapes of diamonds show more color than others do. Shapes like the princess cut are relatively bottom heavy and have more diamond material to look through. Individuals see shades of yellow differently and some shoppers prefer the warm look of the Near Colorless range rather than the cold, whiteness of the Colorless grades.

Another factor that influences diamond color is fluorescence. About a fourth of diamonds have a characteristic that when exposed to ultraviolet light, they glow a color, usually blue. The fluorescence is no longer visible once the light source is removed. The intensity of the fluorescence can vary from Faint, which is barely visible to Very Strong, which is easily visible in a brightly lighted room. A little blue fluorescence can sometimes make Near Colorless diamonds appear even whiter than their true color. Some very strong fluorescent diamonds appear milky or oily in appearance and thus not as clear. The presence of fluorescence in a diamond generally reduces its value with higher levels of fluorescence reducing the value the greatest.

There are some processes, like High Pressure/High Temperature (HPHT) or irradiation, which can alter the color of a diamond. With certain types of brown diamonds, the HPHT process can produce Colorless or Near Colorless color. With HPHT, other types of brown diamonds can be converted to fancy colors like yellowish-green, greenish-yellow, and even shades of pink or blue. Irradiation can result in a variety of fancy colors, even though they are often visibly different shades than natural colored diamonds.

Yellow is the most common and affordable of the colored gem diamonds. There are four color-grades of yellow diamonds with enough saturation to be rated Fancy Yellow; Fancy Light Yellow, Fancy Yellow, Fancy Intense Yellow and Fancy Vivid Yellow. Each deeper shade brings a higher price.

What do these color grades, fluorescence, and color treatments mean to the diamond shopper? There are many color grades between the top D color and J, which is the bottom of the Near Colorless range, with the price of a D being about double that of J color. Most of the difference in price is at the lower color grades where there is also the most visible difference to the eye. The price increase from a J to I can be about 20% while from an E to D is closer to 2%. Diamond shoppers need to examine diamonds with their own eyes so they can determine what color they will be happy with relative to the price.

Most shoppers find that for well cut round diamonds, I color provides a nice, white color and a good value. Fancy shaped diamonds tend not to be as brightly faceted as the round brilliant cut so H color is an excellent choice for value and beauty. However, some shoppers will prefer and can afford higher colors and other shoppers will choose lower colors based on what they find appealing to their eye and their budget.

Avoid diamonds with high levels of fluorescence or any kind of color enhancement unless you specifically want that, have been properly advised, and are paying the lower corresponding price. Beware of jewelry stores who stock larger number of diamonds with fluorescence or will not show you the GIA grading report before you purchase. A merchant who is hiding these factors from you is certainly not someone you want to trust with your important diamond purchase.