x wont go higher than 4bpp!

[Dylan]

y0:
        x wont disply higher than 4bpp. i'm use to typing 'startx -- -bpp 16' in
slack, but when i type that in debian, i get 'error: bpp: unknown option'.
i've alao tried changing my defualt line in /etc/XF86Config to 8, or 16,
but it always stays at 4bpp   ...any ideas?