Available in version 6.1.2 and later.

[Color index 0 = white / color index 1 = black]

[Download so4_23.rgb file and put in $NCARG_ROOT/lib/ncarg/colormaps]

Sample NCL script usages:

;---Using the color map to define colors for contours or vectors
  res@cnFillPalette = "so4_23"
  res@vcLevelPalette = "so4_23"

;---Reading the colormap into an N x 4 (RGBA) array
  cmap = read_colormap_file("so4_23")

;---Using the color map to define a color map for the workstation
  gsn_define_colormap(wks,"so4_23")