In gram strain staphylococcus appears pink because the presence of thick layer of peptidoglycon in their cell walls, which retains the crystal violet these cells are stained with.
If the color of bacteria was purple it means gram positive infection is present but if it appears pink and red then it means gram negative infection is present.Gram stain which is also known as gram's method , is used to classify bacterial species into two groups - gram negative bacteria and gram positive bacteria.
These names found by bacteriologist has christian gram.Most of the proteins is the cytoplasm are normal, so eosin binds to these proteins and stains them pink.
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