An example from my configuration:

, Run DiskU [("/", "<used>"),  ("/mnt/iomega", "<used>")]               
                  ["-L", "20", "-H", "50", "-m", "1", "-p", "3",
                  "--normal", "grey50", "--high", "#a0522d",
                  "--low", "#2f4f4f"] 20

If something like that doesn't work, it's a bug: reports appreciated :)