D colored diamonds are the rarest and totally colorless. Also the most valuable.
SI1 The inclusions in this diamond can be visible at 10x power magnification. Inclusions in diamonds with SI grade clarity might be visible to the unaided eye. SI1 grade diamonds are not as rare as VS1 and VS2 grade diamonds, so they are less expensive and present a great value.
Excellent Make diamond reflects nearly all light thatr enters. Less expensive that an Excellent Make, It still display a good amount brillance and sparkle