Blue diamonds are graded primarily based on the same old criteria used for all diamonds, referred to as the 4 Cs: Carat weight, reduce, clarity, and color. but, for blue diamonds, the coloration grading is specifically vital and is classified primarily based on hue, tone, and saturation. Laboratories consisting of the Gemological Institute of america (GIA) provide an in depth color grading record that specifies the precise coloration and intensity of the blue colour. The maximum precious blue diamonds have a vivid or strong blue colour, loose from secondary colorings like grey or inexperienced.