Bleach it overnight.
Hi this is Peggy. Sorry you are having problems with your toilet. Hope this will help. Removal. To get rid of blue stains in your toilet bowl, use a mixture of 1 cup water and 1 cup ammonia. Before creating the solution, open any windows you can and turn on the exhaust fan so the bathroom is well ventilated.
What Causes a Blue Ring in the Toilet Bowl? | Hunker
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What are you using in the toilet?
Have the stains just recently appeared, or is the staining a result of water not being flushed through the plumbing pipes, such as in a vacant house?