load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"

begin
  wks = gsn_open_wks("ps","color7")    ; Open a PS file "color7.ps"

;
; Change the color map using a predefined color map. See:
;
;   http://www.ncl.ucar.edu/Document/Graphics/color_table_gallery.shtml
;
  gsn_define_colormap(wks,"BlAqGrYeOrReVi200")
;  gsn_draw_colormap(wks)                    ; Draw the color map.
                                            ; Note there's no gray.

  grays = NhlNewColor(wks,(/0.5,0.8/),(/0.5,0.8/),(/0.5,0.8/))
  gsn_draw_colormap(wks)                 ; Draw the new color map
                                         ; You should see 2 grays colors.
end