What is the primary purpose of using a toner in hair coloring?

The primary purpose of using a toner in hair coloring is to neutralize unwanted tones. Toners are typically used after the bleaching process to correct any undesired hues that may arise, particularly yellow or brassy tones. This is especially important for achieving a desired shade of blonde or for refining any color treatment that may not have come out as expected.

Using a toner allows for the adjustment of color, making it appear more polished and true to the intended shade. For instance, if bleaching leaves hair with a strong yellow tint, a toner with a violet or purple base can effectively neutralize that yellow, resulting in a more balanced color.

In contrast, the other options do not correctly represent the primary function of toners in hair coloration. Lightening and darkening hair pertain to the application of hair dyes or bleach, and while toners can contribute to shine, their main role is to modify color tones rather than enhance shine directly.