Nothing is more subjective than beauty.

One should note that the color itself does not play a role in determining whether a natural color diamond is beautiful, as no color among the infinite number of hues and nuances that is found in natural color diamonds can be considered nicer than another. This is entirely a matter of personal taste. What can be said, however, is that the color is by far the most important aspect of a natural color diamond. Cut and carat are only important insofar as they can bring out the best of the color.
Generally speaking, one can say that a good quality natural color diamond is a diamond that has:
-     maximum sparkle and life (i.e. whose cut best brings out its color and sparkle, while at the same time respecting the required proportions)
-     acceptable purity (i.e. no significant inclusion can be seen with the naked eye, and the existing impurities are in harmony with the stone)
-    uniform and harmonious color (there are no areas with stronger or weaker colors - i.e. inconsistencies in the color permeating the stone, which can be the result of an imperfect cut).