In Baldwin's "Sonny's Blues," what are the images of light and darkness, especially effects of characters' dark skin on the white world?

There are so many images of darkness and lightness in
"Sonny's Blues." I think there are such images on every page in the story, and I will
provide a few.  As to the effect of the characters' dark skin on the white world, there
are not many explicit references to this in the story because, for the most part, the
setting gives us African-American characters who are interacting in an African-American
setting, Harlem.

In the very first paragraph of the story,
while the narrator is going home on the subway, he refers to the "swinging lights" of
the car and the faces of everyone "trapped in the darkness that roared outside"
(20.)

In the third paragraph, the narrator refers to
Sonny's face as "bright, and open, there was a lot of copper in
it...(20.)

Moving along to a later section of the story,
the scene the narrator describes in which he last saw his mother alive, he says, "the
night is creeping up outside...," and speaks of "darkness growing against the
windowpanes... (28).  He refers to "the darkness coming and the darkness in the
faces...(28.)  Then the description shifts.  He says,

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"In a moment someone will get up and turn on the
light....And when light fills the room, the child is filled with darkness. He knows that
every time this happens he's moved just a little closer to that darkness outside
(28-29).

In this passage,
Baldwin is alluding to the darkness of the African-American world of that time and
place, when the darkness of being African-American was certainly a consequence of the
effect of the color of dark skin on the white
world.

Another example of the effect of the color of the
African-American on the white world, is the scene in which the narrator's mother
describes how the narrator's uncle was run down and killed by a group of drunken white
men, who surely would never have done this to a white
man.

If you go through the story slowly, you will see
references to lightness and darkness that may or may not be obvious to you because the
words "light" or "dark" are not being used.  For example, Baldwin uses the word "indigo"
(44), which is very deep, dark shade of blue.  Also notice what a nice touch this is, in
keeping with the title of the story, which is about two kinds of "blues," music and
sadness.