The blue staining in the image is due to which dye?

• A. Luxol Fast Blue
• B. Hematoxylin
• C. Eosin
• D. Cresyl Violet

Answer: (A)

Blue color in myelin-rich regions comes from Luxol Fast Blue, a dye that binds to lipids in the myelin sheath. This stain is specifically used to visualize white matter because it highlights the lipid-rich myelin as blue. In brain histology, Luxol Fast Blue is often used with Cresyl Violet to differentiate white matter from gray matter—white matter appears blue, while gray matter (containing neuronal cell bodies with Nissl substance) is tinted differently by the Cresyl Violet. Hematoxylin would color nuclei blue/purple, not the myelin; Eosin stains cytoplasm pink; Cresyl Violet highlights Nissl substance in neurons, typically giving a purple-blue hue in neuronal cell bodies. Thus the blue staining is most consistent with Luxol Fast Blue.