Colorado Cosmetology Written Practice Exam 2026 - Free Cosmetology Practice Questions and Study Guide

A filler should not be used when attempting to enhance hair color because it is intended to fill in gaps and imperfections in the hair shaft. Using a filler when attempting to enhance hair color can result in an uneven or muddy color, as the filler can interfere with the color molecules. The other options, while related to hair treatment, do not directly involve the use of a filler. Improving hair porosity, producing gray coverage, and providing even base color can all be achieved without the use of a filler.