Streptococcus pyogenes is

Streptococci are the gram-positive cocci arranged in chains or pairs. Gram-positive cells have a more acidic protoplasm, which may account for retaining the basic primary dye more strongly than gram-negative bacteria. Gram-positive bacteria are those that resist decolorization and retain the primary stain appearing violet. Reference: Textbook of Microbiology; Anathanarayan and paniker's; 10th edition; Page no: 13, 210