The most valuable and rare diamonds are colorless or have no color. The lack of color enhances the natural prism effect of a cut diamond allowing light to easily pass and be displayed as the colors of the rainbow. Colors range from colorless to fancy yellow with many steps in between providing for very subtle gradations from one value to the next. Diamond color is graded with a letter scale ranging from D to Z.

Those graded from D to F are considered colorless (and rare). Those graded G to J are considered nearly colorless. And those graded K to Z will have noticeable hint of yellow. A diamond with little or no color is more expensive, of course, with the exception of natural (not enhanced) colored diamonds such as canary, pink or yellow diamonds, which can range in the hundreds of thousands of dollars.

The color grading scale is shown below.