Question: could any dye available in the microbiology lab be used in place of nigrosin for negative staining

Answer: No, A simple staining method for bacteria that is usually successful, even when the ``positive staining'' methods detailed below fail, is to use a negative stain. This can be achieved by smearing the sample onto the slide and then applying nigrosin (a black synthetic dye) or India ink (an aqueous suspension of carbon particles). After drying, the microorganisms may be viewed in bright field microscopy as lighter inclusions well-contrasted against the dark environment surrounding them. Note: negative staining is a mild technique that may not destroy the microorganisms, and is therefore unsuitable for studying pathogens.