Treemap change rectangle colours

[alienbuild]

Any advice on how I can selectively change the rectangle colours within a tree map? The documentation to its credit does show how to change for all rectangles ie:

        series.labels.template.setAll({
            fill: am5.color(0x550000),
        });

As well as creating a default or hover state such as:

      series.rectangles.template.states.create("default", {
            fill: am5.color(0x677935),
            fillOpacity: 1
        });

However for my use case i would like to check the value to see if it is a positive or negative number and then change the background based on that outcome (red/green)

Any advice appreciated.

[alienbuild]

I've made some progress using an adapter and it does colour the label backgrounds correctly, however it colours all rectangles with the same color

        series.rectangles.template.adapters.add("fill", function(fill, target) {
            if (target.dataItem.get("value") < 10000) {
                return am5.color(0xb30000);
            }
            else {
                return am5.color(0x50b300);
            }
        });

[alienbuild]

Above code does work, I had a custom theme declared at the start that was overwriting it.