Foreignness was certainly a big theme in 1939, when "De Daumier-Smith's Blue Period" is set. World War II involved a lot of fear of people from other places. This theme recurs throughout the novel, often by showing Jean both resisting and falling into stereotyping foreigners. For example, he obviously admires the M. Yoshoto, yet he can't help looking at him through the lens of the racist novels featuring the so-called Chinese character, Fu Manchu.
Jean also has the experience of being a foreigner himself. He moved to Paris from New York City in 1930 (with his parents) and stayed for nine years. Back in New York City in 1939, Jean longs for Paris, and feels like a foreigner in America. He can't go back to Paris, but he can do the next best thing – go to French speaking Canada, where he is again a foreigner. It is in this foreign setting that Jean is able to break out of his rut of isolation.
Through the Yoshotos, "Blue Period" shows empathy for the plight of the Japanese during Word War II.
Jean's stereotypical portrayal of the Yoshotos suggests that he was a product of racist propaganda.
Since Jean's life-changing experiences happen in a foreign setting, the story suggests that we can only learn by experiencing the unfamiliar.