Colour
 
Diamonds occur in many colours.  Most common colours are yellowish and brown. 

The closer a diamond is to colourless/white, the rarer and more valuable.

Colour is graded on a scale from D (colourless) to Z (heavily coloured). 

Diamonds grades at J and higher will appear relatively icy white.  Below J the diamonds will have a warmer yellowish or brownish tint.