Colored diamonds are valued almost primarily for the intensity and distribution of their color. Learn about the factors that make fancy color diamonds so desirable.
The following article by https://www.gia.edu/ describes the quality factors for fancy colored Diamonds
Fancy Color Diamond Quality Factors
In diamonds, rarity equals value. With diamonds in the normal range, value is based on the absence of color, because colorless diamonds are the rarest. With fancy color diamonds—the ones outside the normal color range—the rarest and most valuable colors are saturated pinks, blues, and greens. In all cases, even very slight color differences can have a big impact on value.
Compared to fancy yellows and browns, diamonds with a noticeable hint of any other hue are considerably more rare. Even in light tones and weak saturation, as long as they show color in the face-up position, they qualify as fancy colors. Red, green, and blue diamonds with medium to dark tones and moderate saturation are extremely rare. See full post here.
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