Colour: The C You Can
Barely See
Colour is graded by comparing a stone, upside down, against a row of master stones under a controlled lamp. You will never look at your ring that way. This page explains what the letters mean, then lines ten diamonds up face-up, in the metal you will actually use, and asks whether you can tell. It applies to natural and lab-grown diamonds alike, with one difference in the money that is covered below.
Colour, in a white diamond, means the absence of colour. The scale runs from D, which has none, to Z, which is visibly yellow or brown. Most engagement ring stones sold in London sit between D and J, and the whole argument happens inside that stretch of seven letters.
The grades were set by the GIA, who started at D so that nobody could claim an "A" stone. Each step is a small, measured increase in tint, judged by a grader holding the diamond table-down next to master stones under daylight-balanced light. Table-down matters: it removes the sparkle, which is what hides colour when you look at a stone face-up on a hand.
That is the whole point of this page. The grader sees the tint because they are trying to. You will see the ring in daylight, in restaurant light, face-up, sparkling, set in metal. The question is not "which grade is whitest?" It is "at which letter does the difference stop existing in the room?"
Lab-grown stones are graded on the same D to Z scale by the same labs, and the line-up below reads the same for them. The difference is supply: growing colourless is now easy, so most lab-grown stones are sold at D to F and the price steps further down, which are for natural stones, shrink to very little. If you are buying lab-grown, colour has almost stopped being a decision.
The line-up below covers D to M, which is where engagement rings are bought. Below M the tint is plain to anyone and the stone is priced as a different thing.
What you are looking at
Ten diamonds in a row, seen from above as you would see them on a hand. They run from D on the left, the whitest grade there is, to M on the right, which is visibly warm. Every one is the same size, cut and clarity. The only thing that changes is colour, and the grade letters are hidden so you judge with your eyes, not the certificate.
What to do: look along the row and tap the whitest stone you would be happy to wear, the point where going further left would not look any different to you. Then try the buttons underneath: the metal changes what the setting reflects into the stone, the size changes how much colour shows, the background changes how easy tint is to see. When you are ready, press Reveal the grades and the panel on the right tells you what you picked and what it would have cost.
The metal decides the grade
A diamond picks up colour from what it sits in. Platinum and white gold reflect white into the stone, so tint shows. Yellow and rose gold reflect warmth into it, which hides tint and makes paying for D to F largely pointless.
Reads as white next to anything but a D on a white cloth. F if you want a margin and the money is there. Going to D or E buys a certificate, not a whiter ring.
The metal's warmth makes I and J look the same as G. Some buyers go to K deliberately for a warmer, older look that suits yellow gold well. Spend the saving on cut or carat.
Rose sits between the two. H to J disappears into the setting. Below J the stone can start to look yellow against pink rather than warm, so stop there.
Three things that change the answer
Size. Colour is easier to see in a bigger stone because there is more diamond for light to travel through. A J at 0.5ct is invisible; the same J at 2ct starts to show in a white setting. The size toggle above exaggerates this on purpose so you can see the direction.
Fluorescence. Around a third of diamonds glow faintly blue under UV, which is in daylight. Faint or medium blue fluorescence in an H to K stone can make it look a touch whiter outdoors and usually comes at a small discount, which is a good trade. Strong or very strong fluorescence occasionally makes a stone look hazy; ask to see it in daylight before you buy.
Lab-grown. Most lab-grown stones are sold at D to F because growing them colourless is no longer hard. If you are buying lab-grown, colour has nearly stopped being a decision; spend the attention on cut instead.
What each step costs
Indicative for a 1 carat natural round, same cut and clarity, against G. Lab-grown follows the same order with far smaller gaps in pounds. The steps are not even: the jump from G up into the colourless band is where the money is, and the steps down from G are where the value is.
- D+35 to 45%
- E+25 to 30%
- F+12 to 18%
- Gbaseline
- Habout 10% less
- Iabout 20% less
- Jabout 30% less
- Kabout 40% less
Three things to ask for
Two stones, two grades apart
Ask to see a G next to an I, face-up, in the metal you are buying. If you cannot tell which is which, you have your answer and you have just saved 20%.
Daylight, not the lamp
Jewellers' lights are cool and bright and flatter everything. Take the stone to the window or the door. That is the light the colour will live in.
The fluorescence line on the report
It is on every GIA certificate. None or Faint is a non-issue. Medium to Strong Blue is usually fine and often a bargain, but look at the stone outdoors before you say yes.