Diamond colour is all about what you can’t see. Diamonds are valued by how closely they approach colourlessness – the less colour, the higher their value. (The exception to this is fancy colour diamonds, such as pinks and blues, which lie outside this colour range.) Most diamonds found in jewellery stores run from colourless to near-colourless, with slight hints of yellow or brown.
A chemically pure and structurally perfect diamond has no hue, like a drop of pure water, and consequently, a higher value. The D-to-Z diamond colour-grading system measures the degree of colourlessness by comparing a stone under controlled lighting and precise viewing conditions to ‘masterstones’ of established colour value.
Many of these colour distinctions are so subtle that they are invisible to the untrained eye; however, these distinctions make a very big difference in diamond quality and price.