Green hair on blonds is not caused by chlorine! Chlorine is a bleaching, oxidizing agent and therefore it lightens hair, not stains it. Chlorine is a contributor to the reaction. The root cause of green hair is copper (above 0.2 pm) in solution becoming oxidized by the sun's UV rays and or the sanitizer (chlorine or bromine), then absorbed by the hair strands, most notably blond hair as its light color shows the green and blue hues better than darker hair. High concentrations can even cause fingernails and skin to turn to a blue to turquoise hue.
Copper can be present in any pool or hot tub. Copper is found in the plumbing like older pools with copper pipe, found in pool and hot tub heaters, and some solar systems which use copper in lieu of plastic for heat exchanger solar panels. Copper may also come from some Ionizer systems purporting to control algae and bacteria. Copper can come from some algaecides which contain the metal. Our pHin mineral purifier also contains copper as its main foundation to help control chlorine usage and algae blooms. Pool and Spa Rx claims the copper is chelated, therefore it will remain in solution and thus not stain.
If you suspect a copper issue, we recommend you get the water analyzed for copper, and if present above 0.2 ppm, start using a product such as Lonza's Sequa Sol to keep the copper in solution and prevent the metal from staining.
For the green hair: Wash the hair in a solution of water and vinegar, or check with a pool dealer to see if they have a special shampoo.