exo-open is for xfce. I do not use xfce. It is better to ask for it in salix forums.
Installing exo (sudo slapt-get -i exo) in slackel the following packages installed also (libxfce4util xfconf libxfce4ui)
Then exo-open --launch TerminalEmulator asked to choose a terminal and then lxterminal appeared. Background is black and letters are white. It is working fine.
Try this.
If you have xterm installed remove it. Then make a link to lxterminal
cd /usr/bin
sudo ln -sf lxterminal xterm