The Clarity
Clarity refers to the number of tiny imperfections, called “inclusions,” present in a diamond. The fewer and smaller the inclusions, the more rare and valuable the stone, which makes clarity a key factor for valuing colorless diamonds. But clarity plays a less important role determining value of a natural color diamond than it does with colorless diamonds. T.he rarity of color is paramount in determining the stone’s value, and the The  color within the diamond frequently makes masks the inclusions invisible to the naked eye.…  
In a white diamond, clarity can make or break the stone. The image above shows a VS quality stone on the left (more valuable), compared to a visibly included, lesser-valued stone on the right.
Now notice the stone on the right, graded as SI1 for clarity, meaning it does have inclusions. But just see what a rich, deep color it displays. A clarity grade of SI1 or SI2 would significantly lower the value of a colorless diamond, but the intensity of color makes this lower clarity stone more valuable and desirable—and far outweighs the fact that the stone has inclusions.