The bands
| Grade | Band | What you see | Best set in |
|---|---|---|---|
| D, E, F | Colourless | No tint at all, even face down | Platinum, white gold |
| G, H, I, J | Near colourless | Nothing visible face up on a hand | Anything. The value zone |
| K, L, M | Faint | Warmth visible face up, especially against white metal | Yellow or rose gold |
| N to R | Very light | Obvious tint | Yellow gold, or avoid |
| S to Z | Light | Clearly yellow or brown | Rarely used in fine jewellery |
The metal changes the answer
This is the part most colour guides leave out. A K colour stone sitting in yellow gold looks fine, because the metal around it is warm and your eye stops registering the tint as a flaw. That same K in platinum sits against a cold white background and the yellow jumps out.
So the practical rule: white metal pushes you toward G or H at minimum, while yellow and rose gold let you drop to K or L and put the savings into cut or carat.
How grading actually happens
Graders judge colour with the stone face down on a white tray, viewed from the side, under standardised lighting, alongside a set of master stones of known grade. That is a deliberately harsh way to look at a diamond, because it strips out the brilliance that hides colour.
Face up, in a setting, with light bouncing around inside the stone, most of that difference disappears. Which is exactly why the grades at the top of the scale command prices that the visible difference does not justify for most buyers.
Fluorescence, briefly
Around a quarter to a third of diamonds glow blue under ultraviolet light. On stones in the faint colour range that blue can actually cancel out some yellow and make the stone look whiter, so medium blue fluorescence on a J or K is often a bargain. On a D or E it can make the stone look slightly hazy in strong sunlight, and it trades at a discount for that reason.
Not sure what you are looking at?
Photograph the stone and the app gives you a visual read on the 4Cs, an estimated value range, and what to check next. Free on iOS and Android.
Frequently asked questions
Why does the scale start at D?
What colour should I actually buy?
Can anyone see the difference between D and G?
Are yellow diamonds low on this scale?
Worth being clear: everything here, and the app itself, is an educational reference. At-home tests narrow things down, they do not certify a stone. Before you buy, sell or insure anything of real value, get it looked at by a certified gemologist or an independent appraiser.