Which of the statements regarding gram staining is wrong?

Q. Which of the statements regarding gram staining is wrong?

1. Mycobacterium tuberculosis stains blue because of the thick lipid layer
2. Streptococcus pyogenes stains blue because of a thick peptidoglycan layer
3. Escherichia coli stains pink because of a thin peptidoglycan layer
4. Mycoplasma pneumoniae is not visible in the Gram’s stain because it has no cell wall

Answer: Mycobacterium tuberculosis stains blue because of the thick lipid layer