{
// just defines a grey color pallete

int ncol=10;
double red[ncol];
double green[ncol];
double blue[ncol];
double stops[ncol];

double dcol = 1/double(ncol);
double gray = 0;
for (int j = 0; j < ncol; j++) {
//   ...... Define color with RGB equal to : gray, gray, gray .......
   stops[j]=double(j)/double(ncol-1);
   red[j]=gray;
   blue[j]=gray;
   green[j]=gray;

   gray += dcol;
}
double totcol=50;

gStyle->CreateGradientColorTable(ncol, red,green,blue,stops,totcol);

}