Kids don’t want to look like 80’s rock stars all swim season. (Well, some do.) This happens mostly to avid and frequent swimmers with particularly dry, fine, light blonde hair.
Copper iron and manganese from algaecide additives and city and well water sources in the water (now in the hair) will oxidize and ”precipitate” temporarily staining very blonde hair green under certain combinations of pH, alkalinity and dissolved minerals.
Pool vendors are discouraged from using metal-based algaecide in the pool but there may certainly be residual from when the pool was set up for the first few years. Copper can be present in local source water too and metals and minerals concentrate over time through evaporation.
If this happens at your community pool, tell your manager so we can work with the pool vendor on reducing metals.
To work on the effects it can have in hair, sources recommend a clarifying shampoo for chlorine/buildup. Examples were Paul Mitchell Shampoo One, Joico KPAK Clarifying Shampoo and Redken Chemistry Shampoo. ION makes a swimmer's shampoo and conditioner sold at Sallys Beauty Supply which another swimmer recommended.
One online article adds, “Removal of the green from ones' hair is a whole 'nuther cup of tea. Depending on how well the color has set into the hair, such as in & out of the pool all day with stressed hair (which chlorine in the pool does cause), is the worst-case scenario, and is very difficult to totally remove in one treatment. But often the use of something acidic, like tomato juice, catsup, or lemon juice, will reduce the metals to their soluble state, and they then can be rinsed out. Be sure to use a conditioner afterwards, or you might end up with something a lot worse than just a green tint.” ...so be careful.
Best prevention for the very susceptible is a more comprehensive plan: Keep hair conditioned and in good health, wet with shower water before going in, not let pool water dry on the hair and to rinse in the shower and towel dry, then do not follow swimming with a typical high pH shampoo like most kids’ shampoos are…
