Clarity refers to the clearness or purity of a diamond. This is determined by the number, size, nature, and location of internal imperfections known as inclusions and external imperfections known as blemishes. While each of the Four C's of Diamond Buying applies to fancy Coloured diamonds, one major difference is the relevance of clarity as it relates to a Coloured diamond's overall quality. While a VS or even VVS clarity is almost necessary when selecting a high quality white diamond, this is not so when considering a Coloured diamond.

Statistically, the occurrence of VS clarity or better occurring in Coloured diamonds is small and those receiving this grading often command a premium in price. The average clarity of a fancy Coloured diamond is generally SI-I. Generally, the most important factor relating to clarity that Coloured diamond dealers consider when purchasing is whether or not a diamond is "eye clean." This is a term used in the jewellery industry to describe a diamond with no blemishes or inclusions that are visible to the naked eye (i.e. a human eye which is not aided by magnifying devices such as a jewellers' loupe or a microscope). The most important thing when deciding on a Coloured diamond is the Colour itself. Coloured diamonds are cut to maximize the Colour, not the clarity. Value is based more so on Colour factors such as hue, saturation and tone. Most inclusions are hidden by the saturation of Colour within a diamond.