Answer:
Purple
Step-by-step explanation:
The cell wall of gram-positive bacteria has a thick peptidoglycan layer present outside the plasma membrane. The gram-negative bacteria have a thin peptidoglycan layer covered by a thicker outer membrane. The outer membrane is absent in gram-positive bacteria.
Given that Staphylococcus aureus and Streptococcus salivarius have a thick peptidoglycan layer and lack the outer membrane, they are gram-positive bacteria.
Due to the presence of a thick peptidoglycan layer, these gram-positive bacteria retain the purple color of crystal violet even after washing with ethanol or acetone.