Guys this is an easy fix -
Go to your My Docs/My Games/GalCiv2 folder and open whichever race config file you need (ex. Terran Alliance.raceconfig)
Look for the line that says < InterfaceColor >0,0,0< /InterfaceColor >
This is XML - 0,0,0 is an RGB color (Red, Green, Blue). 0 is nothing and 255 is all
so 0,0,0 = black; 255,0,0 = red; 0,255,0 = green; 255,255,255 = white; etc, etc..
Change this number to something higher up than 0 and it'll fix your color.
Hint..since you chose black, I'm guessing you wanted to be cool looking. If all 3 numbers are the same, it'll be a shade of grey.
Peace~