Explanation

• The statement that is wrong is: Mycobacterium tuberculosis stains blue because of the thick lipid layer.
• Mycobacterium tuberculosis actually stains red or pink, not blue, due to its unique cell wall composition, which includes a waxy substance called mycolic acid. This makes it resistant to the Gram stain and causes it to appear red or pink.

The other statements are correct:

• Streptococcus pyogenes stains blue because of its thick peptidoglycan layer, which retains the crystal violet dye.
• Escherichia coli stains pink because of its thin peptidoglycan layer, which allows the safranin counterstain to dominate.
• Mycoplasma pneumoniae is not visible in the Gram stain because it lacks a cell wall, making it unable to retain the dyes.