Color variations Polyline property in Google maps API

Question

I have requirement such that I need to draw a line between Sydney, Melbourne and Adelaide and the line between Sydney and Adelaide should be dark in color a

Answer 1

One option would be to create google.maps.Polyline object per every line, below is provided the modified example from Simple Polylines page:

function initMap() {
  var map = new google.maps.Map(document.getElementById('map'), {
    zoom: 5,
    center: {lat: -32.9340105, lng: 128.2698231},
    mapTypeId: google.maps.MapTypeId.TERRAIN
  });

  var flightPlanCoordinates = [
    {lat: -33.877024, lng: 151.227963},
    {lat: -37.816567, lng: 144.961489},
    {lat: -34.930054, lng: 138.593065}
  ];
  var flightPath = new google.maps.Polyline({
    path: flightPlanCoordinates.slice(0,2),
    geodesic: true,
    strokeColor: '#FF0000',
    strokeOpacity: 1.0,
    strokeWeight: 2,
    map: map
  });

   var flightPath2 = new google.maps.Polyline({
    path: flightPlanCoordinates.slice(1,3),
    geodesic: true,
    strokeColor: '#FFCC00',
    strokeOpacity: 1.0,
    strokeWeight: 2,
    map: map
  });
}

html, body {
        height: 100%;
        margin: 0;
        padding: 0;
      }
#map {
        height: 100%;
}

 <div id="map"></div>
 <script async defer
        src="https://maps.googleapis.com/maps/api/js?callback=initMap"></script>

Answer 2

A single polyline has a single set of properties. You can do it with a single google.maps.Polyline for each unique set of properties, so in your example, two polylines.