Available in version 6.2.0 and later.

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

[Download MPL_Blues.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 = "MPL_Blues"
  res@vcLevelPalette = "MPL_Blues"

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

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