Xterm defaults to black text, the foreground color, on a white background. The foreground and background colors can be reversed using the VT Options menu or with the
-rv command line option.
$ xterm -rv
Xterm's foreground color (the default text color) and the background color may be set from the command line, using the options
xterm -fg PapayaWhip -bg "rgb:00/00/80"