Which color is collagen described as in the image using Safran-based staining?

• A. Yellow
• B. Orange
• C. Blue
• D. Red

Answer: (A)

Using Safran-based staining, the colors you see come from how the dye and any counterstain interact with different tissue components. Safranin O tends to color acidic tissue elements, like proteoglycans in cartilage, in a red-pink shade. The collagen fibers, in this particular protocol, are highlighted by the counterstain and the way the dyes distribute within the matrix, which makes the collagen appear yellow. So the observed yellow hue for collagen is a routine result of this staining combination and how it differentiates tissue components.

Keep in mind that other staining methods color collagen differently—Masson's trichrome often makes collagen blue, Van Gieson can render collagen pink-red and muscle yellow, and Picrosirius Red with or without polarization can show collagen as red-orange to yellow depending on fiber orientation and thickness. The key idea is that the color you observe for collagen depends on the staining protocol used.