Ideally, a diamond should be a transparent gem piece. But still, as some of the stones are found with Color, the process of grading through colors become more important. The diamonds are measured on a scale ranging from no Color at all (D) to deeply colored (Z). After ‘Z’, the diamonds are found rich in colors which are popularly known as ‘fancy colors’. The diamonds of popular Color are used as comparison stones for Color grading. A machine called the "Colorimeter" is being used in Color grading at some places but nothing can beat the trained human eye.
As we all know that the valuation of a diamond is not just finalized by its color grade. Hence, sometimes a visible tint in K and above can still be more beautiful and of better value if it carries better clarity and cut. Only diamonds graded N onwards have a tint that is visible through naked eyes. The most popular color tints are combinations of pink, blue, brown, yellow, orange, green and red. Among these yellow is the most common shade while other rare shades are red, blue and green.