berkley review biology questions. pre 2015 (old versions)

[keepSwimmingNemo]

in their explanation they say. the red colored stain is added so the gram negative bacteria can be visualized. the purple colored bacteria also pick up on the red and are now blue. I've never learned it that way. why is it blue.

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[5words]

Why is it blue? because it's gram positive? Whether the stain is Methylene blue or congo red or Safranin, doesn't change the stain on the bacteria (Dark purple/blue / violet for Gram +, and Pink or light red for Gram-). It just that some stain are used to visualized a specific type of bacteria. Such as Safranin, is most used to identify Gram - bacteria.