What is the best color and clarity for an oval diamond?

Could you please elaborate on what constitutes the optimal color and clarity for an oval diamond? Is there a specific grading system that is typically adhered to when assessing these qualities? Are there any factors that may influence one's preference for a particular color or clarity level, such as personal taste or the intended use of the diamond? Additionally, how do the color and clarity of an oval diamond compare to those of other diamond shapes, and how might this affect the overall appearance and value of the stone?