Diamond colour is a measure of the presence or absence of colour in a diamond, and is graded on a scale from D (colourless) to Z (light yellow or brown).
When it comes to white diamonds, the closer to colourless a diamond is, the more desirable and expensive it is.
Other diamond colours e.g. pink, blue, or green aren’t graded on this scale and have their own grading criteria and grading terminology.
This diamond colour guide is part of Jewellery South Africa’s “Diamonds Insights” series. Its purpose is to help you understand diamond colour so you can choose the best colour grade for your next diamond purchase.
In this article, you’ll learn:
- The historical background of the diamond colour scale and why it confusingly starts at ‘D’
- What causes diamond colour
- How diamond colour is graded
- How colour affects the appearance, price, and value of a diamond
You’ll also learn the difference in diamond colour in lab-grown and natural diamonds as well as what to consider when choosing the best diamond colour grade for you.
- Diamond colour measures how white or yellow a diamond is, with the absence of colour being more highly valued.
- The diamond colour grade ranges from perfectly colourless (D) to a light yellow/brown tint (Z). There is no A, B or C grades in diamond colour.
- Perfectly colourless diamonds are the rarest, which is why they’re more valuable and expensive, while diamonds with a brown or yellow tint are considered lower quality and less desirable.
The Diamond Colour Scale
Although diamonds occur naturally in a variety of colour, including pink and blue, we usually tend to think of white diamonds when purchasing engagement rings.
White diamonds are actually very rarely white – the vast majority actually have subtle tints, usually ranging from light yellow to light brown.
Before GIA (Gemological Institute of America) created the diamond colour grading scale used today, there was no universal standard to define diamond colour and no scale to show how a diamond would compare against others.
Some manufacturers would use a grading system from A to C, while others would use numbers. However, these grading methods weren’t applied consistently across every manufacturer in the diamond industry, which made comparing diamonds very difficult.
In the 1950s, GIA created the scale that is now considered the industry standard and is used across all retailers worldwide.
To avoid confusion with the original A to C grading scale, the GIA scale ranges from D to Z, with each letter grade representing a narrow range of colour.
The difference between adjacent grades is very subtle and can be almost invisible to the untrained eye. The most commonly-used colours are in the ‘colourless’ to ‘near colourless’ range:
- Diamonds that are graded D-F are considered perfectly colourless and are awarded the highest grades on the diamond colour chart. Colourless diamonds are incredibly rare and, consequently, are priced the highest.
- Diamonds that are graded G-J are considered nearly colourless – these have very little colour and it can be difficult to see with the naked eye. It can take a trained gemologist to differentiate between colourless and near-colourless diamonds.
- Diamonds that are graded K-M are faint and have a slight colour to them. The larger the diamond, the easier it will be to spot the slight colour.
- Diamonds that are graded N-R are very light and have a faint yellow tint that’s visible to the naked eye.
- Diamonds that are graded S-Z are light and have a noticeable yellow or brown tint, which is why they have the lowest rank on the diamond colour chart.
Now, let’s explore the main factors that affect diamond colour.
What Causes Diamond Colour?
There are two things to consider when we look at diamond colour.
The first is the actual colour of the diamond as it’s graded on its report. The other is the colour that a diamond actually looks, which can be dependent on environmental factors, e.g. the type of metal that the diamond is set into or even the type of light that is shining on the diamond.
The graded colour of a diamond is dependent on the amount of impurities in the diamond. These were present when the diamond was formed and the type and amount will determine the diamond’s colour.
Diamonds can fall into two different categories, depending on the type of impurities they contain: type I and type II diamonds.
- ‘Type I diamonds’ have nitrogen atoms present in them, which can result in a brown or yellow tint. These are the diamonds that are measured on the GIA colour scale.
- ‘Type II diamonds’ don’t have any nitrogen impurities, but there are other elements present that give the diamond its colour. Coloured diamonds fall under the type II category – these are extremely rare but make up a large part of Australian diamond production.
How diamond shape affects colour
Certain diamond shapes can also affect the colour of a diamond – some shapes, like pear or marquise, are more prone to bring out the yellow tint in a diamond, particularly at sharper ‘points’.
Diamonds with broad facets, step cuts or larger tables, like emerald cuts, are known for accentuating a yellow tint or colour present in a diamond.
This H colour emerald cut diamond shows the yellow tint much more obviously than the round brilliant H colour diamond above.
Other shapes can display colour differently in different parts of the diamond, with the areas that are better at reflecting light appearing whiter.
In the H colour pear-shaped diamond below, the section on the right has a similar cut to a round brilliant diamond, which means it reflects a large proportion of the light. This section appears whiter than the pointed end of the diamond which is less effective at reflecting light and which displays yellower tones more obviously.
The lighting conditions that a diamond is viewed under can affect the perceived colour. For instance, a diamond can look whiter under fluorescent lighting but show more colour under diffused lighting typically found at home.
How metal used in a ring’s setting can affect diamond colour
Another factor that can affect the appearance of a diamond’s colour is the colour of the metal used in the setting.
With white metals, like platinum or white gold, it can be a good idea to choose a higher colour grade (H or above) to ensure the diamond appears colourless and doesn’t take on a yellowish hue in contrast with the metal.
However, it’s not necessary to choose the highest colour grades (D, E, or F), as the difference in appearance may be minimal and not worth the extra cost.
For yellow gold settings, the warm hue of the metal can help to mask the presence of some colour in the diamond. In this case, you can opt for a slightly lower colour grade (I or J), as the diamond will still appear relatively colourless against the yellow gold. This can be a more budget-friendly option while ensuring that the diamond doesn’t look yellow.
If we compare an I colour diamond in a white setting and a yellow gold setting, you can see that the diamond in the white colour setting shows the warmer tones of the I colour more obviously:
Similarly, for rose gold settings, the warm, pinkish hue of the metal can also help to disguise some colour in the diamond. Choosing a diamond with a lower colour grade (I or J) should still provide a beautiful appearance without the diamond appearing yellow.
The exact combination of setting colour and diamond can come down to personal preference, but choosing an appropriate colour for the setting can free up some budget to spend on other attributes of the diamond.
How lighting conditions affect diamond colour
The lighting conditions that a diamond is viewed under can affect the perceived colour.
For instance, a diamond can look whiter under fluorescent lighting but look darker and show more colour under direct sunlight which isn’t entering the diamond directly through the top table of the diamond.
Here’s the same diamond in three different lighting conditions:
While this may not affect the colour of diamond you choose, it’s useful to understand that diamond colour won’t always appear the same – a diamond may appear lighter or darker, whiter or more yellow, depending on the lighting conditions.
How Diamond Colour Is Graded
Before we examine how the colour of a diamond can impact its appearance and value, it’s worth understanding how a colour grade is assigned.
Diamond colour is graded by comparing a diamond to a set of ‘master stones’ under controlled lighting and viewing conditions:
Gemologists evaluate a diamond’s colour by placing the diamonds face-down (upside-down from the usual angle from which we see diamonds) on white paper.
By positioning the diamond this way, less white light is reflected through the diamond, which means that gemologists can judge the colour more accurately.
From the top, the colours are quite difficult to see.
When viewed from the side, the diamond reflects less light, which makes the faint yellow much easier to see:
The grading process is repeated several times by different gemologists to ensure that the gemologist’s grading is accurate.
The same diamond can look different when examined from a different viewpoint. Take, for example, this 1-carat G colour round diamond, the top view and the side view look quite different.
How Diamond Colour Affects Price
A diamond’s colour can significantly affect its price and value.
To demonstrate, we’ll compare two diamonds with the same characteristics – 1 carat, excellent cut, VS1 clarity, but different colour grades from a South African diamond specialist.
The first diamond is J-coloured and priced at R78,720.
If we reduce the colour grade to ‘M’, but keep all of the other attributes the same, the price drops to R68,958.
As you can see, the overall pricing difference comes to almost R.10,000.
Once mounted in a ring, these two diamonds would be almost indistinguishable from each other.
Lab Grown Colour vs. Natural Diamond Colour
Both lab-grown diamonds and natural diamonds are graded using the same diamond colour scale, ranging from D (colourless) to Z (light yellow/brown).
While lab-grown and natural diamonds should be chemically identical, there can be a difference in terms of how diamond colour presents due to the difference in how natural and lab-grown diamonds are formed.
There are two methods used to make lab-grown diamonds: High-Pressure-High-Temperature (HPHT) and Chemical Vapour Deposition (CVD). The two methods can result in different ‘undertone’ colours being displayed in a diamond.
HPHT diamonds are grown under extreme heat and pressure conditions that mimic the natural conditions under which diamonds form in the earth. After this initial process, a second heating and cooling process is sometimes applied called ‘annealing’, which aims to improve the diamond’s colour. Diamonds that are annealed may absorb trace amounts of boron during the process, which can give HPHT diamonds a blueish hue.
CVD diamonds, on the other hand, are grown in a specially prepared gas cloud within a chamber, where other trace elements like nitrogen can be present. These elements can cause a brown or grey hue in CVD lab-grown diamonds.
While it’s always a good idea to look for these undertones in lab-grown diamonds, they may not be present at all or may not be visible to the naked eye.
Diamond Colour in South Africa: What You Need to Know
When you’re purchasing diamonds in South Africa, there are some specific considerations to keep in mind.
Among the things you should consider are local certification and grading standards and how these may differ from GIA. In South Africa, the most popular diamond grading labs are the Gemological Institute of America (GIA), the European Gemological Laboratory (EGL), the South African Qualifications Authority (SAQA), and the DIA Grading Laboratory.
It’s common for different diamond grading labs to have slightly different criteria or methods for grading diamonds than international grading labs, which can affect the consistency with GIA and other more common grading reports.
If a diamond you are considering is accompanied by a grading report from a South African lab, it’s always a good idea to discuss colour grades with your jeweller to ensure that it matches your expectations.
Things to Consider When Choosing the Best Diamond Colour Grade for You
We hope our guide on diamond colour helped you get acquainted with the basics of the diamond colour grade and learn how a diamond colour can affect its appearance and value.
Choosing the perfect diamond colour grade for your needs and budget will depend on several factors, including the shape you’re going for, the diamond setting, and its size.
What to focus on:
- Balancing Colour with Other C’s: Colour is just one of the Four C’s (Cut, Carat, Clarity, Colour) of diamond quality. It’s important to balance your preference for colour with these other factors. A diamond with a perfect colour grade but a poor cut can look less brilliant than a diamond with a slightly lower colour grade but excellent cut.
- Consider the Setting: The colour of the setting can influence the appearance of the diamond’s colour. For example, a slightly yellow diamond might appear more colourless in a yellow-gold setting.
- Personal Preference: Remember that the “best” colour is largely a matter of personal preference. Some people prefer the icy coolness of a colourless diamond, while others prefer the warm tones of a diamond with slight yellow hues.
What to watch out for:
- Misrepresentation of Colour: Be wary of misleading language like “blue-white” diamonds. These terms can sometimes be used to make lower grade diamonds seem more appealing.
- Lighting Conditions: The lighting under which you view a diamond can greatly affect its perceived colour. Be aware that some jewellers may use lighting that makes diamonds appear whiter.
- Undisclosed Treatments: Some diamonds may be treated to improve their colour. Make sure any treatments are disclosed, as they can affect the diamond’s value.
Before purchasing a diamond, it’s important that you get acquainted with the 4Cs to make an informed decision and balance the diamond qualities to get more bang for your buck. Doing your own research on the 4Cs is a great way to learn how these diamond qualities interact with one another and will be key to getting a beautiful diamond at a fair price.