The title is significant for the obvious reason that the main character, Pecola Breedlove, longs for blue eyes. She believes that if she has blue eyes people will love her and not recoil from her. If she had blue eyes her mother, Pauline, would hug her with the warmth that she demonstrates to the little white girl whom she cares for. If Pecola had blue eyes Mr. Yacobowski, the candy store owner, would not try to avoid touching her hand while taking coins from Pecola's palm.
There is not much interaction between blacks and whites in the novel, certainly not of the friendly variety, because generally there wasn't much interaction between the groups in 1940s America. Lorain, Ohio, the novel's setting and Toni Morrison's actual hometown, was not part of the Jim Crow South, but it was a town in which there was de facto segregation--that is, blacks and whites would not have interacted. Having said that, the presence of the white supremacist influence is implicit in the title. Morrison uses the superlative "bluest" to demonstrate that Pecola doesn't merely want to claim a piece of whiteness, blue eyes, but that she wants to surpass other blue eyes. She wants to see the world and experience it as the most beloved little white girl would.
It's important that Morrison begins the story in the fall of 1941, which is when the United States entered World War II. The nation's entry was prompted by the Japanese bombing of Pearl Harbor on September 7, 1941. Morrison uses the war, and its fight against tyranny and genocide, particularly in Europe, as an ironic metaphor: why would the United States fight for the liberation of Jewish people and other white minorities in Europe while simultaneously subordinating black people and interning its Japanese citizens? This, Morrison implies, comes from the failure to be white, which makes non-white Americans both vulnerable and burdened by a permanent sense of inadequacy. Pecola Breedlove is the embodiment of this sense of inadequacy which, ultimately, drives her insane.