The Gemological Institute of America (GIA) uses a 12-letter alphabetical scale of D to Z and is used extensively in the diamond trade worldwide. Using this scale, the diamond on scale D have the least amount of color. D is a colorless stone. The diamond at the higher end of the scale Z has deeper tones. The shade of a jewelry is one remarkable of significant worth. The rarest and most significant diamonds are "white" or colorless.
It is recommended to observe color by examining the stone through the pavilion, with the table down.
DIAMOND COLOR GRADE
Diamond Color D-F Grade diamonds have no color, they typically need to be compared to higher or lower graded diamonds to accurately identify the color. D has the highest color grade which are extremely rare and most expensive. The difference between D, E, and F is so slight that only experts can see it when the diamonds are unmounted.
D-F are colorless, exceptionally white, or rare white and the most desirable
Diamond Color G-J Grade Diamonds has very minute traces of color, which can be identified by trained gemologists. When mounted in a setting these diamonds appear colorless to the untrained eye.
G-J are Fine white or Rare white.
Diamond Color K-M Grade Diamonds has faint yellowish tint, it look colorless when mounted. Diamonds of 0.5 carat or more shows traces of color.
Diamond Color N-R Grade Diamonds has very light yellowish tint and appears very “off-white.”
Diamond Color S-Z Grade Diamonds has tinted light yellowish color and appears very “off-white.”