Jaden may have noticed that this question is especially important to you. And as he does not know the world history he has no idea why. When he refers to skin colors etc. on one hand he states something that may be as obvious to him as shoes or golden necklaces. On the other hand he may wonder why his mommy is so special about these questions and so all his phrases are a little test for you.

I think he will better understand when he grows up and I suppose he will be happy about what you taught him.

There is nothing wrong with the fact that people look different and that their genes have a variation that is an indication for where there ancestors came from (BTW in the genetic pool of humanity these are very very small variations). There is a lot wrong with the fact that people think certain kinds of different genes correlate with having lesser intelligence, being more prone to be criminal etc.