GoogleMapAPI のヒートマップの色を変える ref: http://qiita.com/elzup/items/5767dde93cec16724a72

file0.js

    var heatmap = new google.maps.visualization.HeatmapLayer({
            fillOpacity: 1.1,
            radius: 50,
            gradient: ['#fff', '#f00', '#f80', '#8f0', '#0f0', '#0f8', '#08f', '#00f', '#80f', '#f08', 'black']
    });
    heatmap.setData(point);
    heatmap.setMap(map);

file1.js

    var heatmap = new google.maps.visualization.HeatmapLayer({
            fillOpacity: 1.1,
            radius: 50,
            gradient: ['white', '#00f', '#0ff']
    });
    heatmap.setData(point);
    heatmap.setMap(map);