Do people of color sin more than whites? I think people that tend to be racist would believe they do.
No. Sin isn't due to skin color. The Bible teaches that "all have sinned and fall short of the glory of God." (Romans 3:23)
In Genesis 1:27, it says “male and female” he created them. But Eve isn’t mentioned till later in Genesis. So were there other women (and men) before Eve?
Genesis 1 is the "big picture" view of creation. Kind of like seeing creation take place from high up on a mountain. Genesis 2 is a retelling of creation story, but this time from the "ground level" (instead of up on the mountain). So the "male and female" of Genesis 1 and "Adam and Eve" of Genesis 2 are the same people.
Besides God who does the “us” in this passage refer to? 7 Come, let us go down and there confuse their language, so that they may not understand one another’s speech
The "us" only refers to God (just like in Genesis 1:26). God is referring to Himself as Father, Son, and Spirit. Verse 8, of Genesis chapter 11, confirms that the "us" in verse 7 is referring only to God.