Published on13/07/2026
The familiar D to Z scale grades white diamonds on a single criterion: how much yellow tint the stone carries. D is completely colourless and most expensive; the further down, the more tint and the lower the price.
But that scale has an end. Once the colour is saturated enough to pass Z, the stone is no longer graded on the white scale at all. It moves into a different category — fancy colour — and the entire pricing logic inverts: from here, stronger colour is rarer and more valuable.
A faintly yellow W-grade stone is a poor white diamond, and cheap. The same colouring agent a few steps stronger makes a Fancy Yellow, and the price can be many times higher. The boundary between those two worlds is a very narrow band of saturation.
The price of a fancy is set by three factors, in order of importance. First the DOMINANT HUE — pink, blue, yellow, green, red, purple. Second the SATURATION, meaning how strong the colour is, graded Faint, Very Light, Light, Fancy Light, Fancy, Fancy Intense, Fancy Vivid, Fancy Deep. Third, how EVENLY the colour is distributed through the stone.
The rarity gaps are enormous. Yellow and champagne brown are the most common group, accessible in price and readily available. Grey and black are also easy to find. Pink is very much rarer, and since the Argyle mine in Australia closed in 2020 the supply of fine pinks has all but dried up. Blue is rarer still. And of genuine pure reds, fewer than thirty are known to exist worldwide.
Where the colour comes from is worth knowing too. Blue comes from boron in the crystal lattice. Yellow comes from nitrogen. Pink and red come from no impurity at all — they arise from structural distortion of the lattice under extreme pressure, and that is precisely why they are so rare: it is a geological accident rather than a chemical ingredient.
Now the most useful point for a buyer: with coloured diamonds, CLARITY BARELY MATTERS. Strong colour masks inclusions very effectively. A Fancy Vivid Yellow graded SI1 still looks flawless to the naked eye, while a white stone at the same SI1 grade may show a visible dark spot. Paying extra for VS or VVS on a strongly coloured stone is spending money on something nobody will see.
Cut is approached differently too. For a white diamond, the cutter optimises angles to return the most white light. For a coloured diamond, the cutter optimises to DEEPEN THE COLOUR — usually by cutting deeper, making light travel a longer path inside the stone and absorb more colour. That is why fancy colours are so often cut as radiants or cushions rather than round brilliants.
Two warnings before buying. First, colour can be TREATED by irradiation or by high-pressure high-temperature processing, and a treated stone is worth a small fraction of a naturally coloured one. Reports are required to disclose this, so for a coloured diamond a GIA report is not optional but essential.
Second, photographs of coloured diamonds are not trustworthy. Colour shifts dramatically with the light source and the background, and product photography is routinely adjusted to look more vivid than reality. For a purchase at this level, see the stone in person under several different light sources before deciding.