People often wonder why the color grading scale starts at D and not at A. The answer to this is actually a very simple one. At one time, the color scale actually did start at A. In addition to starting at A, color systems were also assigned numbers (0, 1, 2,3), Roman Numerals (I, II, III) and even (AA) . Classifications such as "gem blue". "fine white". "blue white". Were used as color descriptions. These color grading systems were loosely applied and often times, inaccurate and inconsistent. Early on, when the diamond trade developed, diamond grades were developed by various parties within the trade. These original scales never included the letter D and when the Gemological Institute of America (GIA) created the new scale in 1953, they decided to start fresh with a letter that wasn't a part of the previous grading system.
The GIA scale is now the official color grading scale and has universal acceptance among laboratories and trades-people. This current scale ranges from D to Z, with D being colorless to Z which is a light yellow or brown. The term color in regards to diamonds actually increases to its lack of color and the less color a has, the rarer and more valuable it's. Brown or yellow diamonds that have more intense color than Z on the grading scale are considered "fancy colors". These diamonds are graduated by a separate system entirely and this same system is typically used for grading colored gemstones like rubies, sapphires. Emeralds.