Final answer:
Gram-negative bacteria are supposed to appear pink after the Gram stain procedure due to their thin cell wall which does not retain the crystal violet dye and is instead counterstained with safranin.
Step-by-step explanation:
At the end of the Gram stain procedure, Gram-negative bacteria are supposed to have a pink color. This happens because Gram-negative bacteria have a thin cell wall with an outer membrane. During staining, they initially take up the crystal violet dye, turning purple like Gram-positive cells. However, when the decolorizing agent (alcohol) is added, it removes the dye from the thin-walled Gram-negative cells. These now colorless bacteria are then counterstained with safranin, which gives them a pink color.
Gram-positive bacteria appear purple after the Gram stain process as their thick cell wall without an outer membrane retains the crystal violet dye even after the decolorizing agent is applied. This is characteristic of bacteria such as Staphylococcus aureus and cyanobacteria. The iodine in the Gram staining procedure acts as a mordant, forming a complex with the dye that is more difficult to remove from the thick peptidoglycan layer of the Gram-positive cells.