You get chlorine in there and the copper oxidises turning green.
Well water in pool turns green.
Test your swimming pool water.
Your well water probably has some dissolved copper in it.
If the pool has been brushed and shocked it will take a few days to filter out the green and for water clarity to improve.
Other metals you may find in your pool especially when using well water are silver that turns to black iron that turns brown rust and manganese and magnesium that turn to purple when chlorine is added to pool water with compounds of these heavy metals.
This copper can occur naturally in the water or come from copper plumbing that is leeching into the pool.
Use a chemical test kit to test the chlorine and ph levels and determine the extent of the problem.
Shocking a pool should help clear up a green pool if the water is green because of algae or other issues.
Copper turns to a light green color when oxidized by chlorine inside your pool.
Where i live we have lots of iron in the wells and peoples pools turn orange after they add chlorine the first time.
The pool professionals at abc home commercial services can make your life easier by providing regular maintenance as well as troubleshooting any problems that may crop up on occasion such as water turning green overnight.