A computerized system for grading the colour of a diamond, wherein the colour of the diamond is graded based on a predetermined threshold of correlation of colour of a diamond with the colour of a diamond of a plurality of diamonds each having a colour grading assigned thereto, the computerized system including: an optical image acquisition device for acquiring at least a first optical image of a diamond, wherein the first optical image is acquired at a predetermined angle of inclination to the central axis extending normal to the table and through the apex of the pavilion of the diamond and in a direction of towards the table and wherein the first optical image is acquired in an environment having a predetermined constant light level; a processor module for comparing data derived from acquisition of the at least a first optical image with a plurality of data sets each of which corresponds to a diamond of a plurality of diamonds, wherein data sets are each derived from an optical image acquired by an optical image acquisition device in an environment having a predetermined constant light the same as that as (i) and each of the data sets is assigned a colour grading, and wherein said data derived from acquisition of the at least a first optical image and the data of said data sets is data indicative of the colour of the diamond from which it is acquired; and an output module, for responsive to a predetermined threshold of correlation between the data derived from input of the first optical image and one of the plurality of data sets, providing an output signal indicative of the colour grade of the diamond.