It has nothing to do with being any color. I said not afraid of being accused of racism. You are one of the few I admire for saying what you think even if it isn't popular.
I still don't have a thorough understanding of when to hyphenate words and when not to. Is there a universal rule?
I was just joking with the wondering out loud part.
There is not a particularly universal rule about hyphenating words that I can think of to answer what you're asking. In the case of this post, if you had referred to an item or product that is found on, or at the black market, then a hyphen would be necessary because of the descriptive nature of the phrasing.
For instance: "Freida bought a black-market purse and saved $75."
Without the hyphen, the purse is black in color and was purchased at a market, practically any legitimate market, not the under-the-table market where illicit goods are sold.