15. 'Champagne', 'Cognac' and 'Coffee'

What do the terms 'champagne', 'cognac' and 'coffee' mean pertaining to diamond color?

These refer to different types of brown. In the diamond processing/dealing industry, the word 'brown' is considered a killer as far as diamond value goes. Outside the diamond processing/dealing industry, nobody seems to care. Even though champagne the drink is a light yellow color, champagne diamonds are light brown. Congac is usually used to describe a diamond that is orangy-brown or brownish-orange because cognac is a deep golden orange color. Coffee is usually used to describe a diamond that is a deep brown color. Those are dressed-up term the jewelry industry uses to describe brown diamonds. I tend to call them what they are, however. The GIA will call them something like Fancy Intense Brown or Fancy Yellowish-Brown or Fancy Light Brown, etc. I have not seen a diamond grading certificate for a brown diamond that didn't have secondary colors. Whenever I have seen a certificate mentioning brown, it has always been something like Fancy Brownish-Pink, Fancy Brownish-Yellow, Fancy Yellowish-Brown, Fancy Orangy-Brown, and so on. I've never seen a Fancy Brown or a Fancy Intense Brown. I think the reason is that most people with diamonds like this don't get them certified (unless they have a larger stone like 3 or 4 carats or more) because in the world of colored diamonds, brown diamonds tend to fall towards the bottom of the price scale. In other words, most people would not consider it worth the money to get the stone certified. Like I have said elsewhere on this site, the most common gem-quality diamonds in nature are light yellow or light brown. Black is even more common usually as industrial rough and only some black diamonds are faceted, even though they are opaque stones they must first show certain potential.

Reference : http://famousdiamonds.tripod.com/faq.html