This file replaces your alternate_colors.xml file in the T&P data folder. The original is included in the zip as well. I tried to make it selectable on the mods drop-down menu, but it wouldn't cooperate.
This is not a big deal, but I've seen people request other than the original colors, so here's one possibilty.
It changes the white nation unit color to black and the other colors to a more subdued shade of their original. the buildings and mini-map color for the black nation is dark grey.
If you need the bright colors to tell who's who, this is not for you.