function initMap() {
  var map = new google.maps.Map(document.getElementById('map'), {
    zoom: 4,
    center: {lat: -25.363882, lng: 131.044922}
  });

  var marker = new google.maps.Marker({
    position: map.getCenter(),
    icon: {
      path: google.maps.SymbolPath.CIRCLE,
      scale: 10,
       fillColor: 'gold',
      fill: 'gold'
    },
    draggable: true,
    map: map
  });

}

fillColor: 'gold',
  fill: 'gold'