Colour refers to the colour of the diamond and quality a diamond is based on the absence of colour. The colour grading scale from GIA begins with “D” and ends with “Z”. A Colour grade “D” diamond has absolutely no colour and looks pure white. A diamond that has a Colour grade of “Z” will instead look yellow or brownish.
The grading system measures the degree of colourlessness by comparing the diamonds under controlled lighting and precise viewing conditions to established colour sets. However, many of these colour distinctions are so subtle that they will not be visible to most people.
A “Near Colourless” diamond is a safe bet if you plan to set it in a yellow or rose gold setting as the warm colour of the metal makes any colour in the diamond less noticeable. If you want the purest “Colourless” diamond, you may want to set it in a white gold or platinum setting to further bring out the purity.