"Black Friday" was a nickname for the post Civil War slave (had to be paid cash money). Referred to as such because they were usually black and got payed on Friday. "Man Friday" was disfavored because not all of them were men. This title also led to much confusion...for example, the statement, "Black Friday resides in the White House.", made many people turn grey. (just sayin').
Black Friday refers to bookkeeping/accounting. Losses were written in red ink while profits were written in black ink. Black Friday was expected to product such hugh sales that it could put a company back "in the black" after a year of sales losses.
"Black Friday" was rarely trusted with money and history shows...never with a company. For this reason, "Black Friday" often left Saturday morning to go live with, what were known as the "Red Men". Now, the "Red Men" did not observe the days of the week, so it worked out for a little while. It is an often overlooked fact that "Black Friday", "Red Men" and "Yellow Folk" coexisted to create an orangy-black montage that came to be known as Halloween.
When "Black Friday" met "Cyber Monday" they got married and their first child was a robot with what was called "jive". This robot was also known as "Michael Jackson" because his Dad's real name was Jack and his Mom's name was Michelle.
When stores have an increase in revenue, the store is said to be in the black. When they are spending more than they have, they are said to be in the red. Because the stores offer a lot of discounted merchandise the day after Thanksgiving, they have record sales. And that puts them in the black. It has nothing to with race.