Noah’s Daughters-in-law

Assuming human differentiation from Adam on (Acts 17:26), and the probability that 7/8ths of what makes people different today came from the four women on Noah's Ark, could one speculate that Caucasian, Asian and African differences today could have been evident in the wives of Japheth, Shem and Ham, respectively? Wouldn't this help Christian missionaries today make the point that Bible truth is for all people everywhere?

There is no need for speculation here.  Christian missionaries can tell their audiences that the truth of the Bible is for them because that is the Bible’s very message.  I think of the Lord’s promise to Abram:  “…all peoples on earth will be blessed through you” (Genesis 12:3).  I think of Jesus’ words to Nicodemus:   “For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life” (John 3:16).  I think of Peter’s proclamation of the prophet Joel’s message:  “And everyone who calls on the name of the Lord will be saved” (Acts 2:21).  In the Bible God makes it very clear that his love knows no bounds and that his kingdom consists of believers “from every nation, tribe, people and language” (Revelation 7:9).

Abundantly clear passages like these eliminate the need for speculation on how the Bible’s message might be applicable to people everywhere.  The Bible’s message is for everyone.  Christian missionaries—of every kind—seek to share that beautiful truth with everyone.