Diamonds are graded on color, cut, clarity, etc., with the most valuable being colorless and with the fewest flaws.
It used to be that “colored” diamonds- mostly yellow- were less valuable. But, marketers found that calling diamonds “canary” or “chocolate” would increase demand and prices for those stones that people didn’t want in the past. Check out the best LeVian chocolate diamond jewelry selection.
Of course rare colors were/are always worth more, but there are considerably fewer, for example, blue or pink diamonds.
A girl at work has some “black” diamonds.