Melanin in Luxol fast blue when overdifferentiated with lithium carbonate appears which color?

• A. Pink
• B. Blue
• C. Green
• D. Yellow

Answer: (A)

Overdifferentiation with lithium carbonate during Luxol fast blue staining removes the blue dye from pigments that are not lipid-rich, including melanin. Since the tissue is then counterstained, typically with an eosin-containing stain that yields pink, the melanin pigment appears pink. So, when the differentiation step is excessive, the blue color is lost and pink shows up instead. Normal staining would give blue for myelin, but the overdifferentiation shifts melanin to pink.