What is the term for the process of applying color to the hair?

The process of applying color to the hair is accurately referred to as "coloring." This term encompasses a broad range of techniques where pigments are added to the hair to achieve a desired shade or effect, whether for complete coverage, changing the overall color, or adding dimension.

Coloring can include various methods such as single-process color, which involves applying one uniform shade, or more complex techniques that incorporate multiple hues. It's a foundational aspect of hairdressing and is commonly performed in salons to enhance clients' natural hair color or to create bold new looks.

While toning, highlighting, and reflecting are related to coloring, they specify different processes within the broader category. Toning typically adjusts the hue of existing color; highlighting adds lighter strands to create contrast and depth; and reflecting involves adding shine or brightness without altering the base color. Thus, "coloring" is the most comprehensive and correct term for the process described in the question.