Hair goes gray as the follicles' supply of color-producing melanin becomes depleted with age. For most people, gray hairs start to appear in their 30s, but the onset and degree of graying has a lot to do with genetics. In some cases, graying is temporary, with pigmented hair growth resuming after treatment of illness or injury that led to the graying. When dying gray hair, you should change to a lighter color that will easily blend or mask gray or white regrowth. Often, this lightening of the hair requires prebleaching, especially if you are transitioning from naturally dark hair or going blond. Prebleaching softens the cuticle and opens it up so hair dye can penetrate the shaft and last longer.

Prepare bleach mixture in a bowl. Follow the directions for mixing ratios on the powder and developer (ammonium-based hydrogen peroxide) product packaging. Wear gloves and use the opposite end of the brush applicator to mix it into a paste consistency.

Section the hair into four or more parts, depending on the thickness of hair. If you have a lot of hair, separate it into more sections so the mixture can be evenly applied throughout.

Quickly and carefully work your way upward and toward the hairline from the back of your head. Apply lightening paste to the darkest sections of hair first using the applicator brush. This will allow the bleach more time to remove the pigment.

Cover the entire head in the plastic cap to retain heat for processing. This will take several minutes, depending on the formula you use. Check the product instructions for the proper time frames according to desired results.

Rinse hair and wash with a toning shampoo. These formulas usually have a purple tint that helps to neutralize brassiness (orange or yellow tones) left in the hair. Follow with a quality deep-conditioning treatment to restore hair's moisture.