God does not differentiate between nations, status or gender when it comes to salvation.
For you are all sons of God through faith in Christ Jesus. For as many of you as were baptized into Christ have put on Christ. There is neither Jew nor Greek, there is neither slave nor free, there is neither male nor female; for you are all none in Christ Jesus. -- Galatians 3:26–28 (NKJV)
This is the will of Him [God] who sent Me:
that everyone who sees the Son and believes in Him may have everlasting life. -- John 6:40 (ESV)
After this I looked, and there before me was a great multitude that no one could count, from every nation, tribe, people and language, standing before the throne and before the Lamb. They were wearing white robes and were holding palm branches in their hands. And they cried out in a loud voice: “Salvation belongs to our God, who sits on the throne, and to the Lamb.” -- Revelation 7:9-10
For God does not show favoritism. -- Romans 2:11 (NIV), 1 Timothy 2:4
A possible examples of a black people that got converted in the Bible:
- Moses' wife was a Kushite (Ethiopian) (Numbers 12:1).
- The conversion of the eunuch of Ethiopia (Acts 8:26-38).
Ethiopians in Jeremiah's time seems to have black skins according to Jeremiah 13:23 which compares their skin colour with a leopard's spots.