This blog is part of a series “Kids’ Questions Answered,” where we consult the experts to find the best answers possible to children’s confounding queries.

Some folks turn bright red after swimming in the ocean on a sunny day, but lobsters spend their whole lives in the ocean without turning red. Lobsters only turn bright red after swimming in the boiling water of a cooking pot. Why?

Lobsters eat certain plants that contain a red pigment, which serves as a natural paint for the lobsters. The lobsters store that red pigment, known as astaxanthin, in their skins.

However, we see lobster’s blotchy, brownish shells because chemicals in the lobsters’ shells, called proteins, twist that pigment into different shapes. That twisting makes the pigments change colors to either blue or yellow.

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You can’t see it, but living lobsters actually have three layers of colors formed by twisted pigments, according to Michael Tlusty of the New England Aquarium in a video by the American Chemical Society. The actual skin has a red hue. Above the skin, a blue layer forms the first level of the shell. Yellow pigment paints the top layer.

Lobsters’ shells change colors because of the heat of the water. Heat destroys the proteins that twist the pigments. Without the proteins to twist the red pigment into blue and yellow, only the red remains.

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IMAGE: American lobster, Homarus americanus, cooked (Sven Kullander, Wikimedia Commons)