What is the term for the different degrees of lightness and darkness on a page that is important for visual accessibility?

The term that refers to the different degrees of lightness and darkness on a page, which is crucial for visual accessibility, is contrast. Contrast involves the distinction between lighter and darker elements, which enhances readability and ensures that content is easily distinguishable for users, particularly those with visual impairments. High contrast between text and background is essential for clarity, allowing users to quickly and easily engage with the information presented on a webpage.

Balance refers to the arrangement of visual elements, ensuring that they look and feel equal in terms of visual weight. Shade relates more to variations of color, while brightness generally refers to the intensity of light emitted by an object. While balance, shade, and brightness are important in design, they do not specifically address the accessibility concerns that arise from the need for clear visibility, which is why contrast is the most relevant choice.