Which staining reagent is used to make muscle appear blue?

• A. Phosphotungstic acid-hematoxylin
• B. Masson Trichrome
• C. Verhoeff-van Gieson
• D. Oil Red O

Answer: (A)

Phosphotungstic acid-hematoxylin makes muscle fibers appear blue because the phosphotungstate-hematoxylin complex specifically binds to the myofibrillar proteins in muscle, producing a blue chromophore that highlights the contractile elements and cross-striations. This staining choice is used to distinguish muscle from surrounding tissues, since other stains in the list change color differently: Masson Trichrome colors muscle red (and connective tissue green or blue depending on variant), Verhoeff-van Gieson emphasizes elastic fibers (black) with muscle and other components stained in red/yellow, and Oil Red O stains lipids (red) on frozen sections.