This funny sounding title announces several important aspects of the story, namely, sadness, art, and humor.
First, sadness. Even if you don't instantly connect the "Blue Period" with Pablo Picasso (and we'll get to that in a moment), you will probably know that a blue period is a time of sadness, and that somebody in the story probably has the blues. As we quickly learn, that somebody is our narrator. We'll call him Jean, since that's all he gives us.
At the time Jean is writing, his stepfather Bobby is dead, but the actual story is about the period of time just after his mother's death in 1939, which was also an extremely sad time for the world. Now might be the time to head over to "World War II" in Shmoop History. If you click on the timeline you'll see that in 1939 war was breaking out across the world stage.
Jean's blue period coincides with this blue period for the world. In some ways, Jean's period overshadows that of the world, since WWII is never explicitly mentioned. By 1947 (when Bobby dies) the war is over, and the knowledge of what occurred during the Holocaust, and what occurred in the Japanese cities of Hiroshima and Nagasaki (in 1945) washed the world in a sadness that still exists today.
Salinger takes it for granted that readers will know what was going on in 1939, 1945, and the years shortly thereafter. This is called dramatic irony, and means that a reader will know things the character either doesn't know, or doesn't want to talk about. Not only does this make us feel smart, but it also lets us know that there are many layers of sadness to the story, some of them perhaps too painful to be mentioned directly.
As we said, the theme of art is also strongly suggested by the title, "De Daumier-Smith's Blue Period." The paintings from Pablo Picasso's "Blue Period" (1901-1904) were made during what was a sad time for him, due in part to the suicide of his close friend, Casagemas. Most of Picasso's Blue Period paintings feature blue as a dominant color, and are very easy on the eyes, suggesting that beauty and sadness are not mutually exclusive. Not that all the paintings would necessarily be consider "sad" or "beautiful" by all viewers.
If you look at what was going on in Picasso's life during Jean's Blue Period, things get even more interesting. For example, 1939 marked the end of the bloody Spanish Civil War, and ushered in the fascist dictatorship under Gen Francisco Franco." In 1939 Picasso was in self-imposed exile in France, and was actively protesting fascism with his work and words. 1939 is also the year of the death of Picasso's mother – coincidence? We think not.
The title also references another artist not quite so well known as Picasso, Honoré Daumier (1808-1879), French printmaker, painter, sculptor, pacifist, and revolutionary. Daumier is most famous for his political caricatures. This should alert us to the fact that there is also some satire and parody going on in "De Daumier-Smith's Blue Period," as we further discuss in "Genre."