Diamond guides
Fancy Color Diamonds
A diamond with enough natural color stops being a flawed white diamond and becomes something else entirely.
The short version
A different scale, for a good reason
The D-Z scale measures the absence of color, so it cannot describe a stone whose color is the point. Fancy color diamonds are described by hue and graded by how strong that hue is.
Intensity
Faint through Fancy Vivid
The ladder runs Faint, Very Light, Light, Fancy Light, Fancy, Fancy Intense, Fancy Vivid.
Intensity drives price harder than size does. A small vivid stone will usually cost more than a larger faint one of the same hue — the opposite of how white diamonds behave, and it catches people out.
Rarity
Not every hue is equally rare
Yellow is by far the most available. Blue, green and red are vanishingly rare in nature, and a strong stone in those hues is a serious purchase.