For white or colourless diamonds (as opposed to coloured diamonds, which is a whole different story), the diamond industry has adopted an alphabetical colour scale from D to Z, with D as the highest grading. As you go down the scale, the diamond starts to develop a yellow or brown tint. Experts in the world of diamonds determine the colour by comparing a diamond against a master set of diamonds of different colours. Without comparing diamonds side by side, it is very difficult to see the difference between the diamonds. Completely colourless diamonds such as D and E are much rarer than others which is why they come with a higher pricing premium.
D is the highest colour grade attributed to a diamond, denoting that the stone is completely colourless (white);as such, they are extremely rare and command the highest prices.
The colour difference between a D and an E graded stone is usually only visible to an expert gemmologist using master stones as a comparison, although E graded stones are slightly cheaper.
The colour difference between an E and an F is only visible to an expert gemmologist using master stones as a comparison. F grades are the lowest and therefore least expensive of the premium colours.
G graded diamonds are nearly colourless and a slight colour difference only become perceptible when compared to diamonds of grades D or E. G stones appear colourless especially once set and therefore offer excellent value for money.
H coloured diamonds are near colourless diamonds which still appear totally white or colourless if they are not compared side by side with higher colour graded stones. The H colour is generally considered the watershed between colourless diamonds and slightly tinted diamonds.
I coloured diamonds are very slightly tinted diamonds, however, once set in jewellery, these stones may appear colourless. If you are looking to maximize your budget, then an I coloured diamond offers great value for money.
J coloured diamonds are very slightly tinted diamonds, however, once set in jewellery, especially in yellow gold,it is harder to see the slight yellow tint which the J grade produces.
K coloured diamonds are slightly tinted diamonds, however, once set in jewellery, especially in yellow gold,it is harder to see the slight yellow tint which the K grade produces.
L color diamonds have a slightly yellow tone.