A practised eye can recognise the slightest nuances of colour in a diamond. The colours range from colourless to yellow and are graded with a scale from D to Z. D is the highest grade for colourless diamonds. A flawless white diamond is extremely rare, just as are coloured, or so called fancy diamonds. These have tones outside the D to Z colour grades and exist in many different colours such as red, pink, orange, yellow, green, blue, violet, brown, grey and black.
A further quality to consider is the diamond’s fluorescence. This can be seen using ultraviolet light and also affects, i.e. diminishes, the diamond’s value.