Five decades ago, graphic artist Leo Lionni was riding on a train between Manhattan and Greenwich, Conn., with his two young grandchildren, Pippo and Annie. When their behavior suddenly turned from angelic to devilish, Lionni relied on what he later described as “some fast creative thinking.” He took a copy of Life magazine out of his briefcase and ripped out a page featuring a blue, yellow and green design. After tearing the page into small pieces, he used them to tell a story to entertain the rambunctious youngsters. That story became Little Blue and Little Yellow, Lionni’s first picture book, originally published by McDowell, Obolensky in 1959. Next month, Knopf will release a 50th-anniversary edition of the book, which Lionni dedicated to Pippo and Annie.

Little Blue and Little Yellow has had what Janet Schulman, former publisher of Knopf Books for Young Readers and now editor-at-large of Random House Children’s Books, calls a “peculiar history.” Fabio Coen, a friend of Lionni, acquired the book for McDowell, Obolensky, the small New York publisher where he was children’s editor. Several years later, Coen joined Pantheon Books (whose children’s book division eventually merged with Knopf’s) and Lionni followed his editor to that house. Yet the original publisher retained the hardcover rights to Little Blue (HarperCollins licensed the paperback rights) and it has been, in Schulman’s words, “virtually out of print in hardcover for decades.”

Until now. Schulman explains that when she realized the 50th anniversary of the book’s publication was approaching, she decided the timing was right to bring out a new edition of Lionni’s first book. “It is the perfect time to reintroduce this book to the world and to tell how the book came to be—the story of Leo on the train with his grandchildren,” she says. That anecdote is included in a concluding note in the new edition.

It was apparently a fateful train ride indeed. After creating Little Blue, Lionni abandoned the world of commercial art. “Leo was truly a Renaissance man and had many successes before he reached the age of 50,” Schulman recalls. “He had been the art director of Fortune magazine, design director of the Olivetti Corporation of America, and art director of one of the largest advertising agencies in America. He called what happened that day on the train ‘this little miracle,’ that inspired him to give up working in the world of commercial art and devote the rest of his life to the world of fine art and children’s books.”

Leo Lionni.

Lionni, who went on to win four Caldecott Honors and create more than 40 picture books that have sold two million copies in the U.S. alone, certainly relished his new role. Frances Foster became Lionni’s editor at Pantheon when Coen retired around 1980 (since 1995 she has had her own imprint at Farrar, Straus & Giroux). She says that the author created a book a year until the early 1990s. Lionni, who died in Tuscany in 1999, spent half of each year there and half in Manhattan. It was during his months in Italy that he created the art for his books, Foster says. “While he was in Tuscany, we carried on a lively correspondence—in the days of letter-writing,” she recalls. “But none of us saw the fruit of his labors until he came back to the city at the end of the year.”

“He loved the drama of presentation, the unveiling of the new work when he returned to New York every December,” she says. “He’d prop the pictures up against a long wall in the office or in his apartment—under a beautiful Japanese screen—and tell the story, which at that time hadn’t yet been written down but was all in his head and could be followed in the pictures. We then worked closely together to capture the spontaneity and freshness of that telling in a written text.”

What does Foster perceive as the appeal of Lionni’s work? “He wrote about things that matter to children—and to everyone—friendship, getting along, overcoming obstacles, war and peace,” she answers. “He treats his protagonists like characters in a play, the book becomes a stage, and each spread a scene. He is as sensitive to pacing and timing as a theater director.”

And despite the passage of time, she observes, “Kids still identify with his characters. They respond to the rhythm of his language, his playfulness and imagination, the simplicity of action and the logic of his stories. When Little Blue and Little Yellowwas first published, many thought it was too abstract for children to understand, but that was far from the truth. Children had no trouble ‘reading’ Lionni’s abstract shapes and following his story line. They were the first to understand that he was playing with color and shapes to evoke meaning.”

In October, Random House Children’s Books will release the first-ever paperback edition of Lionni’s 1979 Geraldine, the Music Mouse under its Dragonfly imprint. “Reissuing many of his books has been a major undertaking for us for the last few years,” Schulman says. “And we will continue to do this through next year, when we celebrate the centennial of Leo’s birth. He would have turned 100 on May 5, 2010.” That is certainly another noteworthy milestone.

Little Blue and Little Yellow, 50th Anniversary Edition by Leo Lionni. Knopf, $15.99 ISBN 978-0-375-86013-3