Which attribute of color refers to the quality of lightness or darkness?

The attribute of color that pertains to the quality of lightness or darkness is lightness. Lightness describes how light or dark a color appears, which is determined by the amount of light that color reflects. This attribute is crucial in various applications, such as design and art, where creating contrast and visual hierarchy relies heavily on the manipulation of lightness.

In the context of color theory, hue defines the color itself, such as red, blue, or green, while saturation refers to the intensity or purity of the color. These aspects are essential for understanding color but do not directly describe the quality of lightness or darkness. Shade, often associated with adding black to a color, can result in variations in lightness, but it does not define the overall quality of lightness itself. Instead, it refers more specifically to a modified version of a hue that has become darker. Therefore, lightness is the most accurate term when discussing the degree of brightness or darkness within a color.