If cut is considered the most important of a diamond’s characteristics, then color is the runner-up. For this, the GIA uses two scales. The first grades colorless diamonds, also called white diamonds, on a D-to-Z scale. Those graded D are completely clear (and supremely rare), while those at the other end of the range, the Zs, will have a noticeable tint. That said, when a diamond is so deeply hued that it would fall below a Z grade, “We call it ‘fancy’—the point where the color becomes an asset, not a liability, and the value starts to rise,” says Shor.