The first and most obvious device that the author use is repetition. This is obvious when the speaker, Simple, consistently uses the word 'black' as a reference to the point he wishes to make, as in the following extracts:
"...the word black,... I reckon it all started with a black cat meaning bad luck. Don't let one cross your path!
"Next, somebody got up a blacklist on which you get if you don't vote right. Then when lodges come into being, the folks they didn't want in them got blackballed. If you kept a skeleton in your closet, you might get blackmailed. And everything bad was black. When it came down to the unlucky ball on the pool table, the eight-rock, they made it the black ball. So no wonder there ain't no equal rights for the black man."
The text follows this trend throughout and repetition is similarly used in references to the word white. In this instance, though, the writer uses contrast in order to highlight its distinction to black. He alludes to the significant contrasts in connotation that the two words have. Whatever is bad is black, he suggests white people believe, and whatever is good is white.
He proposes that when his day comes - a common idiom suggesting a future time when he is in control or successful - he will turn things around and reverse the connotations that the two words have.
The irony throughout the text is patently obvious and is emphasized in the final paragraph when Simple says:
The earth is black and all kinds of good things comes out of the earth. Everything that grows comes out of the earth. Trees and flowers and fruit and sweet potatoes and corn and all that keeps mens alive comes right up out of the earth––good old black earth. Coal is black and it warms your house and cooks your food. The night is black, which has the moon, and a million stars, and is beautiful. Sleep is black, which gives you rest, so you wake up feeling good. I am black. I feel very good this evening.
It is evident that he believes that the connotations are quite meaningless and without context. The prejudice associated with words is based on a particular mindset informed by prejudice and a generally adopted and irrational stereotype. There is no foundation or evidence to prove that the connotation is, in fact, true.
The last line ends with a rhetorical question a device the author also uses throughout the story:
"What is wrong with black?"
The answer is obvious and easy. The reader's response, however, will be informed by his own subjective understanding of the word derived from what he has learnt or experienced and what he chooses to believe.