The most important thing to know about colour when it comes to diamonds is, in general, the less colour a diamond has, the more valuable it is, all other factors being equal. Diamonds are found in nature in a wide range of colours, from completely colourless (the most desirable trait) to slightly yellow, to brown. So-called ‘fancy colour diamonds’ come in more intense colours, like yellow and blue, but these are not graded on the same scale.

The colour grading system for diamonds uses the letters of the alphabet from D through Z, with ‘D’ being the most colourless and therefore the rarest and most valuable, and ‘Z’ having the most colour within the normal range, and being the least valuable, all other factors being equal. A diamond’s colour is determined by looking at it under controlled lighting and comparing them to the Gemological Institute of America’s colour scale, which is based on a set of diamonds of known colour. Here is a table showing how a diamond’s colour is graded:

A diamond’s colour also has a great impact on its cost. Since ‘colourlessness’ is the most sought-after trait in terms of colour, diamonds that are higher up on the colour scale (e.g. D, E, F) will have a greater value. If a diamond with a specific cut, clarity and carat weight is moved to the next colour grade, it’s possible to see a significant increase or decrease in the per-carat price--all other factors being equal. The idea is to choose a diamond that is as high on the colour scale as your budget will allow, taking all 4C’s into account.

Find out about the ‘Clarity’