A shower filter can help reduce the amount of exposure to chemicals such as chlorine, keeping gray hair from turning yellow. Gray hair tends to pick up pigments from foreign materials more readily than other types of hair, because it has little to no pigment of its own.
In addition to chlorine from shower water or swimming pools, yellowing gray hair can be caused by chemical residue from hair products, sunlight or exposure to pollutants in the air. Along with installing a water filter, it may also be a good idea to wear a hat when outside and wash hair regularly with shampoos intended to remove and prevent buildup.
To neutralize any existing brassy or yellow tones, experts also recommend using a blue- or violet-toned rinse or shampoo. The blue pigments cancel out the warmer color, leaving the hair a neutral grey. However, it is important to not overuse them, as they may leave the hair looking blue if used too often. There are shampoos and other treatments specifically made for grey hair available on the market, and a professional at a hair salon can recommend the right product. In addition, adding silver highlights to grey hair can help add a bright, neutral-toned touch.