Final answer:
After decolorizing a client's hair, a hair dye or colorant is typically used to restore the desired color.
Step-by-step explanation:
After decolorizing a client's hair, you would likely use a hair dye or colorant to restore the desired color. Hair decolorization is a process that involves removing the natural or artificial pigments from the hair shaft, resulting in a lighter or colorless appearance. To achieve the desired color, a suitable hair dye or colorant is applied, which helps restore the pigment and create the desired shade.