Access System.Serializable class from script?

I'm trying to declare by script the following struct:

[System.Serializable] public class GoogleMapMarker { public enum GoogleMapMarkerSize { Tiny, Small, Mid } public GoogleMapMarkerSize size; public GoogleMapColor color; public string label; public GoogleMapLocation[] locations;

}

using

GoogleMapMarker[] markers = new GoogleMapMarker[2];

     markers[0].color = GoogleMapColor.red;
     markers[1].color = GoogleMapColor.blue;

But, I always end up with "NullReferenceException: Object reference not set to an instance of an object" on the line where markers[0] starts...

I had thought I defined it to be an array of size 2, so I am not sure why it is saying null object? Is System.Serializable not accessible from script? Is there another way to do this?