Since a colorless diamond is like a clear window, allowing more light to pass through it than a colored diamond, colorless diamonds emit more sparkle and fire. The formation process of a diamond ensures that only a few, rare diamonds are truly colorless. Thus, the whiter a diamond's color, the greater its value.
Diamonds graded D through F are naturally the most valuable and desirable because of their rarity. Such diamonds are a treat for the eyes of anyone. But you can still obtain very attractive diamonds that are graded slightly less than colorless. Additionally, diamonds graded G through I show virtually no color that is visible to the untrained eye.
If your setting is white gold or platinum, you may wish to opt for a higher color grade than if the setting is yellow gold.