Answer: The trait of sharks being colored white on the underside and blue or gray on top is an advantage for them because it helps them camouflage and blend in with their environment. This is known as countershading. Sharks use countershading as a form of camouflage in the open ocean to help them hide from predators and prey and to make it harder for them to be seen by other animals.
When viewed from above, the shark's darker coloration blends in with the darker depths of the ocean, while the lighter underside blends in with the brighter surface. This makes the shark harder to see and helps it to avoid detection. When viewed from below, the shark's lighter underside blends in with the bright surface of the ocean, while its darker back blends in with the deeper water. This also makes the shark harder to see and helps it to avoid detection.
In addition to camouflage, the coloration of sharks may also serve as a form of communication or identification within their species. For example, some species of sharks have unique patterns of spots or stripes that can help other sharks identify them.
Explanation: blue and gray ;)