There are many ways to treat your hair before swimming to prevent your hair from turning green, but if you forgot to do that before you jumped in the pool, try this! Crush two aspirin (even the cheapest of the cheap aspirin) and mix it into your the normal amount of shampoo you'd use while washing your hair. Lather the mixture into your wet hair and rinse out as usual. Condition and rinse well. It works immediately. Aspirin contains salicylic acid which battles the alkalinity of chlorine to neutralize the green color!