In chapter 12 of Invisible Man, what is the rhetorical purpose of the "spoiled cream" complexions of the women that the narrator sees as he careens out of the subway?

Invisible Man is a novel by Ralph Ellison. The unnamed protagonist is an African American male who experiences a variety of setbacks in life. Similar to the author, the protagonist of Invisible Man grew up in a lower-middle-class household in the Great Plains and was able to attend a prominent college. This background is important to understand, because it allows the reader to gain insights into the perspective of the protagonist.
It is also important to understand the context of the setting and the point in the narrative where this scene occurs. The protagonist, a man from a rural town, enters a subway train in New York City and gets off at a stop in Harlem. Ellison uses the description of the women's complexions to symbolize the protagonist's entrance into the "mecca" of African American culture. He left the predominantly white population of Oklahoma and the social elitism of his college, which was composed of middle class African Americans, and arrived into the heart of black American culture.
The description the protagonist uses could also be a reference to eugenics, which was a popular pseudoscience belief among white supremacists during the early- to mid-20th century. The light-skinned women were too black to be white—hence the word "spoiled," which could mean the tainting of the white race—but were also too light-skinned to be considered black in the eyes of the protagonist. However, in cosmopolitan New York City, the women's complexions are not noteworthy, especially in comparison to how they would be perceived in a rural town in the South.