What is the term for applying color or lightener to new growth of hair?

The term for applying color or lightener specifically to the new growth of hair is referred to as a retouch. This process focuses on the roots where natural hair color has grown out since the last application, ensuring that the color remains consistent throughout. A retouch is typically done to maintain the overall look of the hair color and to cover any gray hair that may have emerged in the regrowth area.

Full color application generally involves coloring the entire head of hair, not just the new growth. Highlighting refers to a technique used to add lighter strands to the hair, creating dimension, while balayage is a more artistic method of hand-painting highlights throughout the hair. Both highlighting and balayage do not specifically address regrowth but rather focus on enhancing the overall look of the hair with lighter tones. Thus, retouch is the most precise term for this particular hair coloring procedure.