Colour
Colour refers to the natural body colour of a diamond and not to the reflection of spectral colours that flash when a diamond moves. Most diamonds naturally exhibit slight hints of yellow, brown, or grey, and so the less colour a diamond exhibits, the higher its value due to the rarity of colourless material. Colour quality is graded via an alphabetical system, ranging from D (colourless) to Z (light yellow). Each letter grade represents a range of colour and is a measure of how noticeable that colour is.