Observe one of the Rev. Dwight Williams' ex-Negro sermons and you will see mostly high yellows and redbones, with only a handful as dark as the Reverend himself. There are very, very few tar-colored people in the pews. It's hard to imagine a bullet, let alone the Word of God, penetrating the skull of
this primitive savage.
Yes, I believe the phenomenon you describe is a sign of spiritual progress for the Hamites. Here is a Bible verse that may be relevant:
Daniel 12:10
Many shall be purified, and made white, and tried; but the wicked shall do wickedly: and none of the wicked shall understand; but the wise shall understand.
However, we must remember that blacks are still black and whites white, and the mixing of the races will only bring about calamity. We should not encourage miscegenation though it may speed up the lightening of the Hamitic tribes. The best we can do is teach them the truth about Christ and let them come to Him, if they believe.