Chlorine can strip your hair and skin of its natural oils. This will make hair very dry and hair will sometimes appear green especially in blondes.
Before getting in a swimming pool wet your hair with shower water, this will help your hair not absorb so much chlorine. The best thing to do would be to wear a swimming cap.
If you are a regular swimmer it would be a good idea to use a clarifying or deep cleansing shampoo. It will help to remove build up and impurities to restore hair.
Some options are:
Joico K-Pak Clarifying Shampoo $33.00
Redken Hair Cleansing Cream $33.00
De Lorenzo Essential Treatments Absolute Deep Cleanser $36.00
Moroccanoil Clarifying Shampoo $42.00