You can change colors and fonts in xterm using the .Xdefaults config file in your home directory. First, open the file.
Next, insert the following lines.
xterm*foreground: #FFFFFF xterm*background: #000000 xterm*faceName: Terminus:pixelsize=14
Finally, refresh the settings with the following command.
That's it. You're now using white on black with the “Terminus” font at 14 points.
More settings are available in the Arch Linux Wiki.