Hair toners are typically used to neutralize unwanted tones in the hair, such as brassy or yellow tones. They are not specifically designed to cover gray hair.

Gray hair occurs when the hair follicles stop producing melanin, the pigment responsible for hair color. To effectively cover gray hair, you would typically need to use hair dyes or colorants that are specifically formulated to penetrate the hair shaft and deposit color. These products often contain ingredients like ammonia or hydrogen peroxide, which help to open the hair cuticle and allow the color molecules to penetrate and bond with the hair.

Hair toners, on the other hand, are usually more translucent and work by neutralizing or counteracting unwanted tones in the hair. They are commonly used after bleaching or lightening the hair to achieve a desired shade, by canceling out any remaining unwanted tones.

If you are looking to cover gray hair, it is generally recommended to use a hair dye or colorant specifically formulated for that purpose. These products are designed to provide better coverage and longer-lasting results compared to hair toners. It's always a good idea to consult with a professional hairstylist or colorist to determine the best approach for your specific hair needs.