Champagne Diamond; the three C’s of Diamond refer to Carat, Colour and Clarity. The Diamond grading for Colour is concerned, basically, with White. D is the whitest of White, then E, then F, then G, then H. H is basic proper White, after which the practiced eye, it is said, discerns “colour” other than White.
Practice in this business means considerable experience, and at the higher end of this business requires a tool that can take many years to fashion, and the tool, for grading colour, is only relevant for judgements of Whiteness.
Coloured Diamonds such as the Champagne Diamond in the above ring fall outside these above-mentioned judgements, devolving to personal rather than professional judgements.
The above Champagne Diamond is a fine Diamond and eye-clean, that is with no inclusions, interior crystal blemishes, visible to the naked eye. It is unique. Plus the 18ct Rose Gold ring setting is itself unique, handcrafted Sydney by a master bench jeweller.

4.68 grams 18ct Rose Gold used in above Sydney-handcrafted ring.