Diamond Color

Since color differences can be so subtle, they are impossible to determine by the untrained eye. To grade a diamond, gemologists often place it on a white background next to another diamond that has been previously graded. 
If all other factors are equal, the less color in a diamond or the higher color rating, the more valuable a diamond becomes. Likewise, as the amount of color increases, the price of a diamond decreases (though this does not necessarily reduce the beauty of a diamond.)