Diamonds come in an array of different colours, such as pink, blue, and yellow, all of which have an effect on price. The rarer the colour the higher the price. Most gem quality diamonds are in the white to yellow spectrum ranging from colourless (the absence of colour) to slightly tinted yellow. These diamonds are graded using the alphabet starting with the letter D for colourless, and then E, F, G...etc as the stone becomes more tinted with yellow. This scale is only used for the spectrum of white to yellow. All other coloured or "fancy" diamonds have their own descriptions such as "Fancy Intense Purplish Pink"!

The differences between the colours are very subtle. For example, if you were to put a D next to an E, you probably wouldn’t be able to see any difference, however when you view a D next to a G you might just begin to see that one is "whiter" than the other. The colours D, E, F, G and H are all within the top white range and can be set in to either platinum or white gold without the contrast of the tint being apparent.

Fluorescence is a phenomenon which can influence how the colour of a diamond is perceived. Approximately 50% of all diamonds, when exposed to long wave ultra violet radiation will glow a bluish colour. This can range from "slight" to "very strong". It is sometimes advantageous to have a certain degree of fluorescence in stones of H colour and less, as this can make the stone appear whiter than it really is. However, strong blue fluorescence in top white diamonds such as "D" colour can make the stone appear a little "milky" in strong sunlight. Strong blue fluorescent diamonds can sometimes be purchased at considerably less than non-fluorescent stones. They are sometimes referred to as "blue/white".