All lobsters turn red when you cook them, but their natural state is a muddy, spotted brown. So Kevin Halton was startled to see a bright red lobster in a shipment he received from Boothbay, Maine.

“I’ve never seen one of these,” said Halton, co-owner of Two Cousins Fish Market in Freeport, “though a few years ago I had a blue one.”

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According to “One in a Million?” published by the Lobster Institute at the University of Maine in Orono, only one in 10 million lobsters is red, making it even rarer than a blue lobster (one in 2 million). Yellow lobsters and calico lobsters — lobsters with mottled orange and black shells — are even rarer: one in 30 million.

Halton and his partner, Tony Terzullie, have named their three-pound visitor Rosie (she’s a female) and they have no plans to sell or cook her. She’ll be hanging out in Freeport until at least Wednesday, July 12, after which Halton plans to send her over to the Long Island Aquarium and Exhibition Center in Riverhead.

Two Cousins Fish Market is at 255 Woodcleft Ave., Freeport, 516-379-0793, twocousinsfishmarket.com