Coston Telegraphic Night Signals were used by the Federals. I doubt that they were used by the Confederates; I've seen nothing in the historical record to suggest that they were. I'd be interested in your references which support their use by the Confederates at Charleston, or elsewhere. Martha Coston sold the patent to the US, and her company manufactured them and sold them to the government during the War. Like blue light, Coston's signals were pyrotechic, but communicated meaning via the variable sequence of red, green and white colors they used. For example, when Housatonic survivors rowed to the USS Canandaigua and informed her captain that their ship had been sunk, he fired rockets to get the fleet's attention, and burned Coston's signal 82, which meant "Assistance, in want of." Blue light such as was reported seen from the Housatonic after she sank, did not communicate any message other than "Hey! Here I am!" or, whatever had been agreed upon between the sender and the observer. The lack of the handheld pistol used to fire a Coston's signal in the recovered Hunley sub further argues that it was blue light, and not a Coston's signal, which was used.