Diamond colour is one of the key characteristics used to evaluate a white diamond. It refers to the presence or absence of yellow or brown tint within a diamond. The less noticeable the colour, the higher the diamond's position on the standard colour grading scale.

The Gemological Institute of America (GIA) uses a D-to-Z grading scale to classify white diamonds based on their colour. D represents the highest colour grade, classified as colourless, while Z represents diamonds with a noticeable light yellow or brown tint.

The same D-to-Z colour grading system applies to both natural and lab grown diamonds. Understanding this scale helps identify the differences between individual diamond colour grades and how colour is assessed.

What Is Diamond Colour?

Diamond colour describes the natural body colour visible in a white diamond. Most white diamonds contain varying degrees of yellow or brown tint, although these differences can be extremely subtle.

A diamond with no detectable colour under standard grading conditions receives a D grade. As the presence of yellow or brown tint increases, the assigned grade moves towards Z.

The GIA D-to-Z scale is the internationally recognised standard for grading colour in white diamonds. Each letter represents a specific range of colour appearance.

Diamond colour is assessed under controlled lighting and viewing conditions to maintain consistency in grading.

Understanding the Diamond Colour Scale: D to Z

The GIA diamond colour scale contains 23 individual grades, divided into five broader categories.

The progression from D to Z represents an increase in the visible presence of colour. However, the difference between two consecutive grades is often subtle and may not be easily identified without professional comparison.

1. D–F: Colourless Diamonds

D, E and F are the three grades in the colourless category. They represent the highest colour grades on the standard D-to-Z scale.

Although D, E and F belong to the same category, they are separate grades. Professional grading comparisons are used to identify these subtle differences.

2. G–J: Near-Colourless Diamonds

G, H, I and J belong to the near-colourless category. These diamonds may contain slight yellow or brown tint, which is generally difficult to identify without comparing them against higher colour grades.

The differences between G, H, I and J are assessed under controlled grading conditions.

3. K–M: Faint Colour Diamonds

K, L and M fall within the faint category. These diamonds show a more noticeable yellow or brown tint compared with near-colourless diamonds.

The degree of colour becomes progressively more apparent from K towards M.

4. N–R: Very Light Colour Diamonds

N, O, P, Q and R belong to the very light category. These diamonds have a more visible yellow or brown appearance than those in the faint category.

The colour in this range is more apparent, particularly when compared with colourless and near-colourless diamonds.

5. S–Z: Light Colour Diamonds

S, T, U, V, W, X, Y and Z are classified as light-colour diamonds. They have a noticeable yellow or brown appearance, with the intensity generally increasing towards Z.

Z is the final grade on the standard D-to-Z scale.

Why Does the Diamond Colour Scale Start with D?

The GIA colour grading scale begins with D rather than A because it was developed to establish a new, standardised grading system.

Before the introduction of the D-to-Z scale, the diamond industry used different methods to describe colour. These included letter grades such as A, B and C, numerical systems and descriptive terms such as blue-white.

The inconsistent use of these descriptions created confusion when evaluating and comparing diamonds.

To establish a distinct grading system without connecting it to earlier classifications, GIA selected D as the starting point for its colour scale.

The D-to-Z system subsequently became the widely recognised standard for evaluating colour in white diamonds.

How Is Diamond Colour Graded?

Diamond colour is graded by comparing a diamond against reference diamonds with established colour grades. This process takes place under controlled lighting and viewing conditions.

Professional grading laboratories follow standardised procedures to minimise external factors that may influence the appearance of a diamond.

The general colour grading process involves the following steps:

1. Controlled lighting

Diamonds are examined under standardised lighting conditions to provide a consistent environment for colour evaluation.

2. Face-down examination

For standard D-to-Z colour grading, diamonds are generally examined face-down. This allows the grader to assess the diamond's body colour while reducing the influence of its face-up reflections.

3. Comparison with master stones

The diamond is compared with reference diamonds known as master stones. Each master stone represents an established colour grade.

4. Colour grade assignment

The grader evaluates the degree of colour present and assigns the corresponding grade on the D-to-Z scale.

The process requires trained professionals because differences between adjacent colour grades can be extremely subtle.

What Factors Affect the Visible Colour of a Diamond?

A diamond's assigned colour grade is determined through standardised grading. However, its visible colour in jewellery can vary depending on several physical and environmental factors.

1. Diamond Shape

Diamond shape influences how its facets interact with light and how its body colour appears when viewed face-up.

Step-cut shapes, such as emerald and Asscher cuts, have larger, more open facets. These facets can make body colour more noticeable.

Brilliant-cut shapes, such as round brilliant cuts, use a different facet arrangement that creates more light return and can make slight colour differences less apparent.

2. Diamond Size

The apparent colour of a diamond can be influenced by its size. In some cases, a larger diamond with a lower colour grade may show its body colour more visibly than a smaller diamond of the same grade.

This is because the amount of visible diamond material and the way it interacts with light can influence colour perception.

3. Cut and Facet Arrangement

A diamond's cut determines the arrangement, proportions and angles of its facets. These characteristics influence how light enters, travels through and exits the diamond.

Cut does not change the diamond's assigned colour grade. However, differences in light return can affect how noticeable its body colour appears.

4. Metal Setting

The metal surrounding a diamond can influence its perceived colour.

The setting can influence the overall appearance of the jewellery, but it does not change the diamond's original colour grade.

5. Lighting Conditions

The lighting environment can affect how a diamond's colour is perceived.

A diamond may appear slightly different under daylight, indoor lighting and artificial lighting. This is why professional colour grading uses controlled lighting rather than relying on ordinary room conditions.

The colour grade recorded in a grading report remains based on the standardised assessment, not on its appearance under every lighting environment.

What Is the Difference Between White Diamonds and Fancy Colour Diamonds?

White diamonds graded on the D-to-Z scale are evaluated according to the presence or absence of yellow or brown tint.

Fancy colour diamonds are classified separately because they display distinct and more pronounced colours.

These colours can include yellow, pink, blue, green, orange and red.

Unlike the standard D-to-Z scale, fancy colour diamonds are evaluated using a separate grading system that considers their colour characteristics.

The D-to-Z scale should not be used to describe the full range of fancy coloured diamonds.

Are Natural and Lab Grown Diamonds Graded Using the Same Colour Scale?

Yes. Natural and lab grown diamonds are evaluated using the same D-to-Z colour grading system.

Both are made of crystallised carbon and have the same fundamental chemical composition and crystal structure. Their primary difference is their origin.

Natural diamonds form beneath the Earth's surface over geological periods, while lab grown diamonds are produced in controlled laboratory environments using specialised growth processes.

Lab grown diamonds can be available in different colour grades depending on their growth conditions and any subsequent treatments.

The grading system evaluates the diamond's colour characteristics, not whether it was formed naturally or grown in a laboratory.

What Diamond Colour Does Onya Offer?

Onya offers lab grown diamond jewellery featuring D–F colour diamonds. These grades belong to the colourless category of the GIA D-to-Z colour grading scale.

D, E and F are the three highest colour grades in this category. They represent diamonds with no noticeable yellow or brown tint under standard grading conditions.

Onya uses D–F colour lab grown diamonds across its fine jewellery collections, including lab grown diamond rings, engagement rings, bracelets and men's diamond jewellery.

The colour grade of an individual diamond can be verified through its applicable grading documentation and product specifications.

Frequently Asked Questions 

• Which diamond colour is best?
  D colour is the highest grade on the GIA D–Z scale. D, E and F are classified as colourless diamonds.

• Which is the real colour of diamonds?
  Diamonds in their purest form are colourless. However, natural diamonds can have varying degrees of yellow or brown tint due to trace elements and structural characteristics.

• Which colour diamond is the most expensive?
  D colour diamonds generally command the highest prices among white diamonds when other characteristics are comparable.

• Do real diamonds look blue?
  Most white diamonds do not appear blue. Some diamonds exhibit blue fluorescence under ultraviolet light, while naturally blue diamonds are a separate fancy colour category.

• What is the best colour scale for diamonds?
  The GIA D–Z scale is the widely recognised standard for grading white diamonds, with D representing colourless and Z representing light yellow or brown.

• What diamond colour is better, E or D?
  D is higher than E on the grading scale. Both are colourless, but D has the highest possible colour grade.

• What is the cheapest diamond colour?
  Z is the lowest grade on the standard D–Z scale and generally costs less than higher colour grades when other characteristics are comparable.

• What diamond colour does Onya offer?
  Onya offers D–F colour lab grown diamonds, which fall within the colourless category of the GIA diamond colour grading scale.

• Are Onya diamonds colourless?
  Yes. Onya offers D, E and F colour diamonds, which are classified as colourless under the GIA grading system.

• Are Onya lab grown diamonds IGI certified?
  Onya offers IGI-certified lab grown diamonds. Refer to individual product details and grading reports for specific diamond certification information.