What is the term for the color that remains in the hair after fading?

The term "undertone" refers to the subtle hue that remains in the hair after the primary color has faded. In hair color, while the dominant or primary color is what you see first, the undertone can significantly influence the overall appearance of the hair. Undertones are typically warmer or cooler shades that exist beneath the surface of the hair color and can affect how the color is perceived, especially as it fades over time.

Understanding hair color involves recognizing that the primary color may change with environmental factors, washing, and time, while the undertone provides a consistent base that remains. Common undertones in hair color include ash (cool), golden (warm), and neutral tones, which can help stylists adjust hair color formulations to create desired results and maintain the integrity of the color throughout its lifespan.