The development of the D-Z diamond colour grading scale by Richard T. Liddicoat at the GIA (Gemological Institute of America) in the 1950s was a significant step forward in standardising the assessment of diamond colour.
Starting at D was a deliberate choice by the GIA to distance themselves from previous systems and emphasize the importance of neutrality. The impact of settings on diamond colour perception is also crucial to note, with factors like metal type influencing how colours are perceived. Additionally, the fancy-coloured diamonds, which are rare and highly prized, offer a range of unique and captivating hues based on the presence of impurities.