Bl 3rd standard establishes the classification of diamonds, according to the color and the number of imperfections they present. Diamonds of intense color, such as those called fantasies, have been excluded from this standard. The "over blue", "petrole", etc. filings have also been excluded, as they are all diamonds of very variable quality and therefore difficult to place in a classification.
IRAM 16 506-1962 history
1962IRAM 16 506-1962 Diamond classification based on penetration and color