KXL_SetDrawColor -- A point, a line, and the color at the time of a frame clearance are set up.

void KXL_SetDrawColor(Uint8 red, Uint8 green Uint8 blue);

#include <KXL.h>

int main(void)
{
  KXL_CreateWindow(100, 100, "sample", 0);
  KXL_SetDrawColor(0x55, 0xee, 0x88);
  KXL_DrawRectangle(30, 30, 30, 30, True);
  KXL_UpDateImm(0, 0, 100, 100);
  getchar();
  KXL_DeleteWindow();
  return 0;
}