Leaflet marker/icon help

It looks strange that you add both a GeoJSON layer from result.geojson and a marker created from [result.lat, result.lon].

If result.geojson contains the same point information as [result.lat, result.lon], you are adding both markers to your map.

an event listener and change the icon through setIcon() method:

createdMarker.on("dblclick", function(evt) {

        var myIcon = L.icon({
            iconUrl: 'res/marker-icon-red.png',
            shadowUrl: 'res/marker-shadow.png'
        });
        this.setIcon(myIcon);
});

Or you can get some help from this Tutorial