Determining diamond colour is a very subtle art. So many diamonds look perfectly colourless to the naked eye, which makes it hard to distinguish between the varying degrees of colouration. Nevertheless, diamond colour is an important factor in determining the value of a diamond. These tiny variations have quite an impact on the overall appearance of the diamond.
The Gemological Institute of America uses a scale that goes from D –. Z to determine diamond colour. A D-coloured diamond is considered colourless. A Z-coloured diamond is considered light yellow. For the most part, the closer a diamond is to a rating of D, the more it's worth. The reason for this has to do with the purity of the light that's reflected from the diamond. A colourless diamond will reflect all the shades of whole, white light equally. Acting like a prism, it'll produce dazzling colours as it turns in the light. A yellow diamond favors the yellow wavelengths of light. Doesn’t give as brilliantly lustrous an appearance as it’s colourless cousins.
There are diamonds that are coloured more intensely than the D-Z scale accounts for. These are called fancy colour diamonds. These are diamonds of any colour (did you know that diamonds come in every colour?) that have very high colour saturation levels. These are of higher value than diamonds in the lower alphabet range of the D-Z system.
Diamond colour affects the price quite substantially. For a 1 carat diamond with a clarity rating of VS1 starting at a color rating of K, the colour breakdown would look like this: Moving the colour rating up to H will add approximately $1,700 per carat to the price of a diamond. From H to F, the price increase is another $1,100 per carat. From F up to D (the highest rating, colourless) the price increase would be an additional $900 per carat.
A quick tip for men who are shopping for diamonds for their future spouses. Take a woman you can trust with you. For the most part, women are more sensitive to the subtle differences in colour than men are. It’s not a rule. It does tend to hold true in most situations.