Symbolism, Imagery, Allegory
The narrator's first job is in a highly patriotic paint company most famous for its Optic White paint color. Whee-oo! Whee-oo! Symbolism alert! When a novel explicitly about the weird and evil lines drawn in the name of racism mentions white paint, you just know things are about to get crazy symbolic.
In any case, in order to create this pure white, the narrator is instructed to—get this—add ten black drops of toner into each bucket:
"Now measure ten drops into the paint…There, that's it, not too goddam fast. Now. You want no more than ten, and no less."
Slowly, I measured the glistening black drops, seeing them settle upon the surface and become blacker still, spreading suddenly out to the edges. (10.48-10.49)
Could this possibly have anything to do with black/white relations in America? We think so, too.
We think that this paint business demonstrates the necessity of the black contribution to white America —although many people in Invisible Man think of America as a white man's country, America would not be America without the contributions of black people.
Taking another angle, the name "Liberty Paints" is ironic since it implies freedom for all... which is clearly not the experience of the narrator throughout this entire story.