The True Colours (Blue Spread)

Here's the C code which generated this dataset:

  for (int b=0; b<256; b++) {
    for (int ra=0; ra<16; ra++) {
      for (int g=0; g<256; g++) {
	for (int rb=0; rb<16; rb++) {
	  fprintf(f, "%c%c%c", b, g, (ra<<4)|rb);
	}
      }
    }
  }