The diamond colour refers to a lack of colour or hue in a diamond. The transparent or colourless diamonds are graded “D” which is the highest and the most expensive. Here the term “Colour” refers to pale yellow colour in white diamonds. It shouldn’t be confused with “Fancy Colour Diamonds”, such as intense yellow, pink or blue.
The colours of white diamonds are graded on a scale using the letters of the alphabet from D to Z. The letters essentially correspond to the level of colour in the diamond, the rarest being in the 'colourless' range. The closer up the alphabet towards D, the fewer colours there is in the diamond. The closer along the scale you get towards Z, the more yellow is in the diamond.
After cut, colour is generally considered the second most important characteristic when selecting a diamond, because the human eye tends to detect a diamond's sparkle first and then its colour. The illustration below shows the different grades of colours in brief:
“D” colour is regarded as totally colourless or transparent diamond and therefore the most expensive diamond. The lowest colour grade is “Z”, which has yellow colour visible clearly by naked eye. The detail of different grades of diamond colour is described in the chart below:
Another characteristic that does not affect the colour grade of a diamond but is worth keeping in mind is diamond fluorescence. When choosing a diamond, you should always look for a fluorescence of either none or faint. Medium, Strong and Very Strong fluorescence can make some diamonds appear to have a slightly blue or milky white tint in strong sunlight or under an ultraviolet light.
What Colour to Choose?
For absolute perfection, look for colourless diamond with a grade of D-F for a diamond with no discernible colour.