You'd be looking for a dye that survives in the blood and urinary tract and imparts blue/green colors to the urine and that isn't reactive or toxic. And genera

You'd be looking for a dye that survives in the blood and urinary tract and imparts blue/green colors to the urine and that isn't reactive or toxic. And generally speaking, when you are looking to treat something in a double-blind test, the control isn't placebo, it's the standard treatment. It's a tricky enough problem that when double blind studies have been done, the control will generally simply have a lower dose of methylene blue rather than no dose.