Which of the following is NOT a function of hair color products?

Hair color products serve several primary functions in enhancing and transforming hair appearance. Covering gray hair is a fundamental purpose of these products; they provide a uniform color that effectively obscures white or gray strands, allowing for a more youthful look. Creating highlights is another function, as hair color products can be used to add dimension and brightness to the hair, enhancing its visual appeal with lighter shades. Altering the hair's natural color is a core purpose as well; these products allow individuals to change their hair color altogether, whether for aesthetic reasons or personal expression.

Moisturizing the scalp, however, is not a primary function of hair color products. While some formulations may include moisturizing agents, the primary aim of hair color products is to provide color, rather than to condition or hydrate the scalp. Therefore, recognizing that the focus of hair color products is on changing and enhancing color rather than scalp care clarifies why that choice is not considered a function of these products.