Color Grading Scale

Checking your diamond’s report card.

Diamonds come in virtually all colors of the rainbow, from the “beautiful violet” of the Hope diamond to shades of blue, brown, gray, orange, etc. But colored diamonds are very rare and precious. Chances are, all the diamonds you’ll see in your diamond shopping will be white or yellow, and the whiter the better.

The yellow color in diamonds comes from nitrogen, and as a rule, the more yellow the stone, the less value it has. There’s a good reason for this. The yellower the stone, the less sharp and sparkly it appears. A whiter stone lets more light pass through it, making it sparkle and shine.

The exception to the rule is the canary diamond, which is a beautiful bright yellow and very expensive. Some people are more sensitive to the color of diamonds. What may appear slightly yellow to you may look clear to another person, so it will take a higher color grade to satisfy you.

The best way to judge the color of a diamond is to compare it to a master set or a colorimeters. A master set of diamonds has been graded in a laboratory. A colorimeter is a devise that grades the diamond automatically without the need of human eye participation.

Either ask the jeweler for a set and compare the diamonds you’re thinking of buying with the diamonds in the master set or have the jeweler place the diamond in the colorimeter to get an accurate grade.

FRED’S ADVICE: Go for grades H or I. Once mounted, they’ll look just as good to the average person as the higher grades, without costing a bundle. The average diamond purchased in the U.S. is color grade M or N, but the customer is usually told it’s higher.


D, E, F: Colorless

G, H, I: Nearly colorless

J, K, L: Slightly yellow

M, N, O: Light yellow

P, Q, R, S, T, U, V, W, X: Darker yellow

Z: Fancy colors

Even though there are several grades in each category, there are slight differences between the letter grades. D is the clearest and most valuable, X is a dingy yellow and least expensive. Z grade and beyond-colored diamonds-are the rarest and most expensive.



Fluorescence is a diamond’s reaction to ultraviolet (UV) light. Some diamonds glow in different colors under UV light, and the general rule is to avoid them. If you put a diamond under UV light and it glows strong blue, the diamond may look dull in the sunlight. Diamonds with strong fluorescence may be worth up to 20% less than diamonds which do not fluoresce. Faint fluorescence which doesn’t fog the diamond is OK.


Phosphorescence is a type of photoluminescence related to fluorescence. A phosphorescent diamond also reacts to ultraviolet (UV) light, but instead of immediately emitting a glow when ultraviolet light is present, the diamond will absorb some of the radiation from the light and emit it even after the exposure of the UV light is over. Translation: phosphorescent diamonds can look poor (foggy and hazy) outdoors and continue to look poor for hours later even though the diamond is no longer being exposed to harmful UV rays. Metaphorically, we could say a phosphorescent diamond is susceptible to sunburn. Not a good thing.


Corresponding grading means matching clarity grades with color grades. For every clarity grade, there’s a color grade that corresponds, or makes the best match in determining value. Diamonds that have corresponding grading sell for higher prices originally, and they also appreciate in value more than diamonds that don’t, and therefore have higher resale value. Buying a diamond with non-corresponding clarity and color grades is like buying a pink Porsche: it’s okay as long as you don’t try to resell it. The market for pink Porsches just isn’t as good as the market for, say, red Porsches.

Here’s a list of clarity grades and their corresponding color grades. Notice that for each clarity grade there’s a perfect match, and a high and low color that also works well.




D (Perfect) — 10.00%

E (Low)


D (High)

E (Perfect) — 9.25%-9.99%

F (Low)

VS1, VS2:

F (High)

G (Perfect) — 8.50%-9.24%

H (Low)

SI1, SI2:

H (High)

I (Perfect) — 6.50%-8.49%

J (Low)


No corresponding color grades

The value of a stone is always based on the lowest clarity or color grade and its highest corresponding grade. For example: let’s say you purchased a stone with a clarity grade of SI1 and a color grade of G. You can see above that G is not a corresponding color for an SI1 stone. The SI1-G diamond will cost you more than the SI1-H, but will appreciate no more over time than the SI1-H.

When you don’t correspond the grades — say you buy high clarity and low color, or high color and low clarity — you’ll never get your money back for the higher grade. For example, an SI1-F would resell no higher than the value of an SI1-H, and a VS1-I would resell no higher than the value of an SI1-I. A diamond that is not correspondingly-graded could be expected to appreciate 2% to 4% per year.

by Fred Cuellar, author of the best-selling book “How to Buy a Diamond.” More questions? Ask the Diamond Guy®