PanelExpanderButton color change?

GoJS
1

How to change panelExpanderButton color
$(“PanelExpanderButton”, “LIST”, // the name of the element whose visibility this button toggles
{ row: 0, alignment: go.Spot.TopRight}),

2 
        $("PanelExpanderButton",
          {
            ...,
            "ButtonBorder.fill": "cyan",
            "ButtonIcon.stroke": "red",
          })