MRIcro ships with a color scheme called 'aal.lut' that describes the
red/green/blue values for each region. The format of the file 'aal.lut' is
the ImageJ colorscheme format (shared by ImageJ, MRIcro and XMedcon). It is
very simple:
 -Data saved in binary format, 8-bit bytes
 -Each LUT file is 768 bytes long:
  1.) bytes 0..255 RED values for indexes 1..256
  2.) bytes 256..511 GREEN values for indexes 1..256
  3.) bytes 512..767 BLUE values for indexes 1..256

I suspect that you assumed that the data was saved with all three colors
for each index (RGBRGBRGB....), but the data is stored in a planar format

I hope this helps.