Diamond colour, or more accurately, the lack of colour, plays a vital role in determining the value and beauty of a diamond.

Definition of Diamond Colour

• Colour in Diamonds: Refers to the presence or absence of colour in white diamonds. The less colour, the higher the quality.
• Natural Fancy Diamonds: Diamonds that exhibit intense colours like blue, red, or green. They have a different grading system and are not included in the standard diamond colour scale.

The GIA Colour Grading Scale

The Gemological Institute of America (GIA) developed the most widely accepted colour grading system, which classifies diamonds from D (colourless) to Z (light yellow or brown).

• D-F: Colourless
• G-J: Near Colourless
• K-M: Faint
• N-R: Very Light
• S-Z: Light

Factors affecting Diamond Colour Perception

Diamond Size: Larger diamonds show colour more prominently than smaller ones.

• Shape: Some shapes, like emerald and asscher, show more colour than round or oval shapes.
• Setting Colour: The metal in which a diamond is set can either mask or emphasise its colour. For example, yellow gold can mask some yellowish hues, while white gold or platinum might make them more evident.

Technical Grading Process

Diamonds are graded for colour by comparing them to a set of master stones under controlled lighting conditions.

• Controlled Environment: Standardised lighting (usually daylight equivalent) and neutral backgrounds.
• Master Stones: A set of real diamonds representing each color grade.
• Positioning: Diamonds are viewed from the side (not the top) to prevent brightness and reflections from masking the true colour.

Diamond Fluorescence

Fluorescence refers to a diamond's ability to emit visible light when exposed to UV radiation.

• Impact on Colour: Some diamonds with strong fluorescence might appear whiter in UV-rich environments, like sunlight. However, very strong fluorescence can sometimes make diamonds appear hazy.
• Fluorescence Grading: None, Faint, Medium, Strong, Very Strong.

Factors Affecting Diamond Colour Pricing

• Rarity: Colourless diamonds (D-F) are rarer and thus more valuable.
• Perception: Diamonds in the G-H range are popular for offering near-colourless appearance at a reduced price compared to D-F diamonds.

Advanced Tips for Professionals

1. Grading Consistency: Always use a consistent and controlled environment to ensure colour grading accuracy.
2. Fluorescence Balance: When choosing diamonds, consider the fluorescence. A diamond with slight yellowish hues (like J or K) might benefit from medium fluorescence.
3. Side Stones: When diamonds are set alongside others, ensure they have comparable colours to prevent contrast discrepancies.

Brown and Grey Overtones

• Some diamonds may have brown or grey overtones affecting their colour grade. It's essential to identify and communicate these overtones, as they can affect a diamond's value and appearance differently than pure yellow tints.

Certification

• Ensure diamonds come with certifications from reputable labs, specifying the colour grade. This offers assurance to buyers and sets industry standards.

Understanding diamond colour's technicalities is crucial for professionals in the industry. It's not merely about discerning shades but understanding how various factors like shape, setting, size, and even fluorescence play into colour perception and value. A nuanced grasp of diamond colour can significantly influence decision-making, both in purchasing and selling scenarios.