In art, the term that describes the brightness or dullness of a color is "Value." Value refers to how light or dark a color is. It is the degree of lightness or darkness of a color in relation to a scale from white to black.
Understanding value is crucial in creating depth, contrast, and visual interest in artworks. By manipulating the value of colors, artists can create a sense of three-dimensionality and mood in their pieces.
For example, in a black and white photograph, the variations in shades of gray represent different values. The more gray a color has, the lower its value, while the closer a color is to white, the higher its value.
So, in the context of the question, when discussing the brightness or dullness of a color in art, the term to use is "Value."
