The bluish eyes tell us that the snake is almost ready to shed its skin. The old skin is separating from the new skin underneath. It makes the snake's overall color duller, but it especially shows up on the eye scales. That is right. Snakes have scales over their eyes. This protects them from scratches and from drying out, since snakes do not have eyelids, and can't close their eyes. As the old eye scale separates from the new eye scale that is growing underneath, the light is refracted. This lets us see a bluish haze over the eye. It also severely restricts how much the snake can see, which tends to make them very anxious about any movement. Just before the snake starts to shed its skin, the eye scale will totally separate, which makes it clear again, making it easier for the snake to look for a rough surface to rub against to help it crawl out of its old skin.