Now the Bible doesn't say what the mark is, but some have tried to say that Cain became the first black man. Of course, that theory only explains two colors and does not consider the flood bringing the human race back to one family. I don't believe this theory because I don't think any color of people are cursed and it only explains two colors. Perhaps all families, countries, nations, and tongues were created or developed from this event. Maybe the colors were divinely created at that time, or maybe they are just a natural product of a small group of people speaking their own language and marrying back to their own parent stock.
Racial traits become more pronounced in a small inbreeding group.
The Bible isn't clear on this subject. These four theories are the only ones that I know. I prefer the Tower of Babel explanation. I know the Bible does say in Acts 17 that all nations are of one blood so there is no reason for anyone to be a racist.