Swimming in chlorinated water and exposure to sunlight for long periods of time will affect all hair color. Whenever possible, it is advisable to wear a swim cap, and shampoo your hair as soon as you can after your swim. If you swim frequently, you may also need to reapply Grecian 5 more often. It is also a good idea to wear a hat or a cap when in the sun. You may also want to use a shampoo or conditioner containing a sunscreen (UV protectant).