Colour is one of the fundamental attributes of a diamond and colour grades actually refer to how colourless or “white” a stone is. Diamond colour is graded according to the GIA* colour scale, from D to Z, where D is rated as the most colourless, and therefore the most sought after and costly.
Further down the scale, the colours become more yellow and finally brown. However, to the untrained eye, there is little variation in the D-H range and therefore slightly lower grades provide much better value for money while not necessarily appearing vastly different. Stones graded I and below alter in colour and any diamonds graded J and below will be slightly tainted.