如何动态更改sigma.js设置？

<script src="sigma.min.js"></script>

var graph = new sigma({
  container: 'graph-container'
});

graph.addNode({
  id: 'node1',
  label: 'Node 1',
  x: 0,
  y: 0,
  size: 1,
  color: '#ff0000'
});

graph.addEdge({
  id: 'edge1',
  source: 'node1',
  target: 'node2',
  color: '#000000'
});

graph.settings({
  defaultNodeColor: '#ff0000',
  defaultEdgeColor: '#000000'
});

graph.refresh();

graph.settings({
  defaultNodeColor: '#00ff00',
  defaultEdgeColor: '#0000ff'
});

graph.refresh();