I am using a

Here is main part (used UIButton instead of FluentUI.Button for simplicity):

Anything(UIButton(type: .system)) {
    $0.setTitle("Try me!", for: .normal)

    $0.addTarget(toggleColor, action: #selector(Action.perform(sender:)), for: .touchUpInside)
    toggleColor.action = {
        isGreen.toggle()
    }
}

Complete test module is here