A Guide to Diamond Colour

The diamond colour scale is the universal standard for grading a diamond's colour. It begins with the letter D and continues, with an increasing presence of colour, to the letter Z, which represents light yellow, light brown or light grey.

As you move down the scale towards Z, subtle hints of colour become more apparent, affecting the stone's overall appearance. The most highly regarded white diamonds are completely, or close to completely, colourless. Many Ralph Karouni diamonds range between D and G, the rarest and most sought-after grades, allowing more light to pass through the stone and further enhancing its brilliance.

Established in 1931, the GIA is a public-benefit, non-profit institute renowned for its gemmological research. It protects consumers through analysis, education and gem grading, and sets global quality standards. The GIA developed the definitive diamond colour scale in the early 1950s, when many different and subjective terms were used to describe a diamond's colour, leading to inconsistency.

To avoid confusion, the creators of the scale began with the letter D, a grade that had not traditionally been associated with top-quality diamonds. The 23 colour grades on the GIA scale are divided into five subcategories:

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

While colourless or white diamonds are typically composed of carbon atoms arranged in a crystal lattice, coloured diamonds owe their vibrant hues to trace elements or structural irregularities during their formation, including pressure, temperature and radiation exposure.

Coloured diamonds are exceptionally rare, with only one in ten thousand exhibiting intense colouration, and their grading is a complex, highly specialised process. The GIA grades coloured diamonds on a scale evaluating the intensity of their colour, from faint to fancy deep. The rarest and most valuable fall into the Fancy Vivid category, displaying an intense, pure hue that is truly mesmerising.

Ralph Karouni has been the custodian of rare coloured diamonds of remarkable character. Discover our high jewellery creations featuring fancy coloured diamonds.

Different diamond cuts influence how the colour of a stone is perceived. A round brilliant cut is associated with concealing colour, its facets maximising the light that passes through the stone and making slight hues less noticeable. In contrast, cuts such as the emerald cut have long, open facets that can make any traces of colour more apparent.

The size of a diamond can also affect the perception of colour. Diamonds of a higher carat weight have a greater surface area, making colour imperfections more visible. As the carat size increases, you may consider a higher colour grade to maintain a colourless or near-colourless appearance.

When selecting a diamond, it is important to consider the interplay between shape, setting and carat weight in relation to colour, as each factor influences how colour is perceived. Our diamond experts can guide you to understand the nuances of a diamond's colour, and every Ralph Karouni diamond is meticulously evaluated against the 4Cs as prescribed by the GIA.