How do I clean paint and glue from bluestone?
Muriatic could be a bit harsh, causing a 'bleached' spot. Many natural stones are sensitive to acids, most being alkaline (from types of limestone).

A "citrus" paint stripper could be less harsh, but it is acidic, also.  

I would use ammonia and a soft nylon hand brush, alternating after rinses with a mild detergent.