Black, in folk culture, has many meanings, only some applying to race. Some of the following references to black I found interesting, but not necessarily pertinent.

Pot calling the kettle black- both were heated over open fire in the past, hence both became blackened.

In the old horse operas, the villain wore a black hat, to provide visual distinction from the hero in the pure white Stetson. When these films were made, both characters were white.

A black cat may be a witch. A very old superstition in Europe, but it also was found among slaves. Did they pick it up from whites or is the superstition African as well?

This is digression, but interesting- In South Carolina (late 19th c.), Negros, when speaking of crows and the corn crop, said, "If he come, he no come; if he no come, he come." It meant if the crows came, the corn would not be allowed to grow, and if they did not arrive the corn crop would be all right (JAFL, vol. 8, no. 30, p. 252).

The dark is often treated like black in superstitions. One from Connecticut- Comb your hair after dark, come sorrow to your heart.

The Black String:
A powerful love-charm. It is composed of a strip of skin from the body of a man who has committed suicide for love; "it must be 'peeled from the head to the heel and back without crack or split'." The charm, known in New York, is Irish in derivation (JAFL, 1895).

The Jay-bird and the Martin.
It was once a common belief in the South (both Black and White) that the jay-bird was never to be found on Friday, because he visits Hell on that day. That's a whole nuther tale, but it comes up in the following tale (much abbreviated here) collected from from Virginia Af-Am story-tellers (1890's).
A jay had a nest near to a martin's nest. The jay would steal the martin's eggs when the martin was away. The martin said, "Something is carrying away my eggs. I wish you would notice for me when I am not at home, and I will do the same for you when you are gone off." "I will," said the jay.
The martin goes off, and the jay waited until the martin was in sight, and begins to look around, spotting a crow. "Here he is, out here in the tree," says the jay.
"All right," said the martin; "I will go out there and see him. Come and go, Mrs. Jay."
"No, no, I will watch for another while you are gone."
Mr. and Mrs. Martin go out to see the crow. "Mr. Crow, said Mr. Martin, "Mr. Jay said you were at my house today."
"Where is your house?" asked the crow.
"Yonder, where you see that little round house on the pole."
"I have never been there in my life," said the crow; I will go and see the jay about it."
On a Friday morning the crow goes to see the jay. "Hello," said the crow.
"Mother is not here," said one of the young jays.
"Where is she?" asked the crow.
"She went to carry some grains of sand to hell."
"When she comes, tell her Mr. Crow was here to see here."
When the jay came, the young bird said, "Mother, a big black man has been here to see you."
So the jay moved to another home the next day.