Many sellers grade champagne diamonds on an informal C1-C8 scale. C1 is the lightest, faintest brown, and C8 is deep, rich, saturated brown. The middle of the range, around C3 to C5, is where you often find that glowing honey tone. C1-C8 is industry shorthand, not a lab standard. Formal lab reports use the D-to-Z scale with brown color modifiers, or fancy-color grades, instead.