Changing the weight of a memory card when zooming?

Question

Here is my small map of Tallinn with three sources:

As you can see, in this example of the card there is no "red" part.

But when I zoom out, I get the following:

I need my heatmap to have an orange-yellow-green color when you zoom out, not red.
How can I achieve this with Heatmap and google-maps-api(optional).

Note:
I did a zoom out event to change the radius, I think this event can also help me solve this problem, but I don’t know which configurations should be changed:

google.maps.event.addListener(map, 'zoom_changed', function() {
    var zoomLevel = map.getZoom();
    heatmap.setOptions({radius:zoomLevel*0.5});
});