Which stain is capable of staining collagen in reddish orange?

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

Answer: (A)

Stains color tissue elements differently based on their chemical affinities, so you can pick out collagen by the color it yields. Phosphotungstic acid-hematoxylin gives collagen an orange-red color, a reddish orange that stands out against other components stained by the same slide. This distinct hue comes from the phosphotungstic acid interacting with collagen, making it easy to identify collagen fibers under light microscopy. In contrast, Masson Trichrome colors collagen blue (or green in some variants), Verhoeff-van Gieson renders collagen yellow to pink, and Oil Red O stains lipids red. So the reddish-orange appearance of collagen points to PTAH staining.