Which of the following is a primary purpose of active ingredients in cosmetics?

The primary purpose of active ingredients in cosmetics is to deliver therapeutic effects. Active ingredients are the components in cosmetic products that are specifically designed to change the skin's structure or function for the better, addressing particular skin concerns such as acne, dryness, or signs of aging. These ingredients are carefully selected and formulated to have a therapeutic impact, such as hydration, exfoliation, or even the provision of sun protection.

The other aspects, such as providing color, promoting preservation, or enhancing fragrance, serve different purposes within a cosmetic product. Color additives are primarily for aesthetic appeal and do not necessarily contribute to the skin's health. Preservation ingredients are meant to extend the shelf life and maintain product safety, while fragrance enhancers are there to improve the sensory experience of the product rather than offer any therapeutic benefits. Each of these roles is important in the formulation of cosmetics, but they do not equate to the direct health benefits provided by active ingredients.