How to change the icon of createOptionForm icon on select field ?

->createOptionAction(
    function (Action $action) {
        $action->icon(null);
        $action->color('primary');
        $action->label('Create Candidate');
        $action->link();
    }
)

->createOptionAction(
    function (Action $action) {
        $action->icon(null);
        $action->color('primary');
        $action->label('Create Candidate');
        $action->link();
    }
)