The colour of the diamond refers to the lack of intrinsic colour found in a stone. Most diamonds will appear devoid of colour, but there will always be hints of either brown or yellow. The more yellow the stone, the lower its quality and lesser its worth.
The issue of diamond colour has been one of great concern of specialists for centuries, and this lead to the development of a definitive colour scale in the 1950s by the Gemological Institute of America. This widely adopted scale starts with D (highest quality) and ends with Z (lowest quality). The exclusion of A - C allows for the future proofing of the scale against the potential discovery of even higher quality stones.
As with any diamond property, it is a balancing act, and there are a number of other factors you need to consider whilst you search for the perfect match for yourself:
Diminishing Returns: To the untrained eye, there will be no discernible difference in diamonds in the D-F grades. This means that if you’re looking to make a trade-off, then dropping down a grade is often a great way to compromise.
Colour Matters In Heavier Stones: This is fairly straight-forward, so if you’re looking to opt for a large carat then you will be well-advised to choose a higher colour quality grade as well.
Shape Can Hide Colour: The highly reflective quality of stones with more facets, allows them to do a better job at hiding small hints of colour. If you’re concerned about the colour of your stone, then opt for a round rather than a square cut.
Gold Can Compliment Colour: Yellow gold will make subtle traces of colour much harder to detect. This gives you another area that you need to consider when you’re trying to strike the perfect balance as you search for a piece that will be on your finger for the rest of your life.
Be Aware Of Fluorescence: Small to medium fluorescence will only be visible to an expert who is viewing your stone under UV light, so it isn't necessarily a major hurdle as it first appears to be. Having said that, fluorescence reduces the quality and the look of the diamond and it can cause a blue glow to be emitted from the stone.