* Concentration of Peroxide: Lower concentrations (like in some hair products or diluted household peroxide) might lighten gray hair slightly over time, making it appear more brassy or yellowish, especially if the hair already has some yellow tones. Higher concentrations (like those used in hair dye developers) can lighten the hair more significantly, potentially making it a lighter, brighter gray or even almost white.
* Exposure Time: The longer the peroxide is in contact with the hair, the more color it will remove.
* Porosity of Hair: Gray hair tends to be more porous, meaning it absorbs liquids more easily. This can make it more susceptible to the effects of peroxide.
* Underlying Pigment: Even gray hair has some underlying pigment. Peroxide will affect this pigment, which can lead to different shades of lighter gray, yellow, or brassy tones.
In summary, peroxide can lighten gray hair, but the result isn't always predictable or desirable. It can sometimes lead to brassiness or an uneven tone.
If you are looking to change the color of your gray hair I recommend visiting a licensed hair professional.