It is the lack of color, or whiteness in a diamond that allows the light to pass effortlessly through the stone and disperse that beauty back to the observer. Color is not so much white versus yellow, as the chart tends to indicate. It is more light versus dark. A white diamond will look very clean, crisp, and brilliant. A yellow diamond will not really look yellow, as it will look darker and dirty, without nearly the same brilliance.
Clarity refers to how many flaws, or inclusions, are in the diamond.
In most cases, clarity has very little to do with the beauty of the diamonds. Rather it effects how the diamond looks under the microscope. To determine a diamonds clarity grade, it must be examined under 10x magnification. Whatever minute inclusions there may be make every diamond unique. These are nature's fingerprints and in most cases do not mar the diamond's beauty nor endanger in durability.