How to Create a Text File List of RGB Values in C http://mikequentelsoftware.blogspot.ca/2010/11/how-to-create-text-file-of-rgb-values.html

rgb.c

#include <stdio.h>

int main() {

  FILE *fp;
  fp = fopen("true_colour.txt", "w");

  int r = 255;
  int g = 255;
  int b = 255;

  for (r = 255; r >= 0; r--) {
    for (g = 255; g >= 0; g--) {
      for (b = 255; b >= 0; b--) {
        fprintf(fp, "%d", r);
        fprintf(fp, ",");
        fprintf(fp, "%d", g);
        fprintf(fp, ",");
        fprintf(fp, "%d", b);
        fprintf(fp, "\n");
      }
    }
  }

  fclose(fp);
  return 0;

}