Re: Why does chlorine cause blond hair to turn green?

This answer was provided by a chemist who works in the personal-care products industry, and specifically with hair.

When hair turns green after exposure to chlorine, it is usually because the hair has been damaged in some way, typically by color treating or perm-ing. These treatments leave behind residual ammonium chloride (NH₄Cl). This substance, in turn, forms a complex with copper ion (Cu²⁺) to give the complex

NH₄CuCl

It is also possible to have interactions with shampoos that will cause chlorine to turn hair green, but formulators generally stay away from anything that could complex with chlorine in that way.

This problem may usually be remedied by switching to another hair care product.

Of course, the green color is more noticeable if the person has blond hair, but the same reaction occurs with all hair colors.  In summary, this behavior actually has nothing to do with hair itself but results from chemical interactions between products used on the hair.

The study of compounds such as these complexes is an important part of chemistry, and specifically what is called inorganic chemistry You can probably find more information about inorganic chemistry either in your high-school chemistry book or a freshman college chemistry textbook.