During the Antiquity, Nubia was a kingdom south of Egypt, in an area corresponding to current Sudan. Ancient Egyptians called this land Ta-Seti, or Bow land - a reference to the characteristic weapon used by the Nubians. Nubia was forcibly annexed by New Kingdom Egypt, but regained its independance and became the kingdom of Kush.
As for the Libyans, it is not so obvious to depict the Nubians accurately, and the skin color is also a matter of debate.
Searching the net (again), I found these documents:
Nubians on a wall painting in Beit El Wali (Nubian temple in the region of Asswan).
Nubian prisoners, Tomb of Horemheb, Saqqara Necropolis
The Nubians seem to have varied skin colors, from brown to very dark brown - if not an artistic licence, since the light and dark skins on the relief (second picture) are regularly distributed.
Once again, I tried to be pragmatic and simple: most illustration show the Nubians as black people with a dark brown skin, I chose that option.
Here you are the result:
The same minis, but with a different daylight (picture taken earlier in the morning):
