#include <graphics.h>
      void setpalette(int colornum, int color);

      setpalette changes the colornum entry in the palette to color. For
      example, setpalette(0,5) changes the first color in the current palette
      (the background color) to actual color number 5. If size is the number of
      entries in the current palette, colornum can range between 0 and (size -
      1).
      You can partially (or completely) change the colors in the EGA/VGA
      palette with setpalette. On a CGA, you can only change the first entry in
      the palette (colornum equals 0, the background color) with a call to
      setpalette.
      The color parameter passed to setpalette can be represented by symbolic
      constants which are defined in graphics.h.
      Name         Value
      BLACK        0
      BLUE         1
      GREEN        2
      CYAN         3
      RED          4
      MAGENTA      5
      BROWN        6
      LIGHTGRAY    7
      DARKGRAY     8
      LIGHTBLUE    9
      LIGHTGREEN   10
      LIGHTCYAN    11
      LIGHTRED     12
      LIGHTMAGENTA 13
      YELLOW       14
      WHITE        15
      setpalette cannot be used with the IBM-8514 driver; use setrgbpalette
      instead.

      /* setpalette example */
 
      #include <graphics.h>
      #include <stdlib.h>
      #include <stdio.h>
      #include <conio.h>
 
      int main(void)
      {
         /* request autodetection */
         int gdriver = DETECT, gmode, errorcode;
         int color, maxcolor, ht;
         int y = 10;
         char msg[80];
 
         /* initialize graphics and local variables */
         initgraph(&gdriver, &gmode, "");
 
         /* read result of initialization */
         errorcode = graphresult();
         if (errorcode != grOk) {  /* an error occurred */
            printf("Graphics error: %s\n", grapherrormsg(errorcode));
 
            printf("Press any key to halt:");
            getch();
            exit(1);               /* terminate with an error code */
         }
 
         maxcolor = getmaxcolor();
         ht = 2 * textheight("W");
 
         /* display the default colors */
         for (color=1; color<=maxcolor; color++) {
            setcolor(color);
            sprintf(msg, "Color: %d", color);
            outtextxy(1, y, msg);
            y += ht;
         }
 
         /* wait for a key */
         getch();
 
         /* black out the colors one by one */
         for (color=1; color<=maxcolor; color++) {
 
            setpalette(color, BLACK);
            getch();
         }
 
         /* clean up */
         closegraph();
         return 0;
      }

setrgbpalette

  no output of example at the moment
  do not hesitate and add it...