Could you use Congo red for positive staining or crystal violet for negative staining?

Congo red is primarily used as a negative stain, as it binds to the polysaccharides in the cell wall of certain bacteria, resulting in a red appearance against a blue background. Crystal violet, on the other hand, is commonly used for positive staining; it is the primary stain in the Gram staining procedure, where it stains the peptidoglycan layer of Gram-positive bacteria, turning them purple. Thus, Congo red is not suitable for positive staining, while crystal violet is not typically used for negative staining.