The GIA 4Cs Colour Scale for diamonds is indeed the industry standard, ranging from D (colourless) to Z (light yellow or brown). The value of diamonds increases as they approach colourlessness, with less tint of yellow or brown being preferable. However, as you mentioned, there are exceptions with fancy colour diamonds, which possess distinct and intense colours outside of the D-to-Z range, such as pinks and blues. These fancy coloured diamonds are valued differently due to their rarity and unique appearance.
While many of these colour distinctions may not be readily apparent to the untrained eye, they significantly impact the quality and price of diamonds. This highlights the importance of grading diamonds accurately to ensure fair valuation and informed purchasing decisions in the jewelry market.
