Which technique is utilized to enhance the color of hair that has already been filled with highlights?

The technique utilized to enhance the color of hair that has already been filled with highlights is glazing. Glazing involves applying a semi-permanent or demi-permanent color over the hair to add richness, depth, and shine, enhancing the overall appearance of highlighted hair. This process does not lighten the hair; instead, it works to refine and amplify the existing tones, helping to create a more vibrant and cohesive look.

Glazing can also help to neutralize any unwanted undertones that may have arisen from highlighting, ensuring a more balanced color finish. It is particularly effective on highlighted hair, as it can revive the color and keep the hair looking fresh and healthy without the need for more permanent color changes.

Other options either do not specifically address the enhancement of highlighted hair or pertain to different aspects of hair color treatment. For example, gray reduction deals with covering or mitigating gray hair rather than enhancing highlights. Fur light is not a standard term in haircoloring practice, and color on color implies a different technique where new color is directly applied to existing color rather than enhancing highlights specifically.