Answer:
The answer is the thickness of the peptidoglycan layer.
Explanation:
Gram-positives have a simple cell wall with a thick layer of peptidoglycan which fixates the crystal-violet and KI complex while gram-negatives don't. Then when the destaining is done with alcohol, the gram-negatives are washes while the gram-positives are permanently stained. The last step is staining the gram-negatives with safranin which will happen but it will not be washed, and also it will not fixate in gram-positives.
