Which technique is utilized when applying multiple colors to achieve depth in hair?

The technique utilized when applying multiple colors to achieve depth in hair is dimensional haircolor. This method involves the strategic placement of different shades to create contrast and visual interest, enhancing the overall appearance and texture of the hair. By using various tones, dimensional haircolor gives an illusion of movement and volume, making the hair look fuller and more vibrant.

In contrast, single process haircolor involves applying a single shade to the entire head, which does not provide the depth and complexity that multiple colors can achieve. Special effects typically include techniques like highlights, lowlights, or ombre, but they are usually applied sparingly or in a more dramatic fashion rather than focusing on overall dimension. Temporary haircolor is often used for short-term changes and does not inherently involve layering multiple colors for depth. Thus, dimensional haircolor remains the preferred technique for achieving this goal.