COLOUR
One of the 4Cs used to grade diamonds, colour in fact refers to lack of colour.
The most highly prized and valuable stones are entirely colourless, clear as pure
water. Diamonds are graded along a GIA scale, from D down to Z, the lowest
grade. Alongside D, which is perfectly colourless, E and F grade diamonds are
also classified as colourless, G-J are near colourless, while grades K-Z contain
varying degrees of noticeable colour.