No, Crystal violet cannot be used as an alternative to Nigrosin stains to perform negative stains. You can stain whatever you want, but not bacterial cells. This enables chemists to see the cell in its natural form (unstained) and study their morphology more closely, (their shape, and their arrangement in group). The cells on their surface had an overall negative charge, do by their nature, they are only meant to attract only positive charges. Therefore, since Crystal violet has positive charges, it will adhere to the cell surface and stain it. Which is usually not the intention for carrying out negative staining.