In QuickGraph, when exporting to graphml, how do I specify the edge color?

Question

I'm updating a method that exports a graph from .dot to .graphml format.

Previously, colors and labels were set in the FormatEdge and FormatVertex events. I am not clear on where to set the color for graphml.

.Dot Way

...
public ExportDot()
{
  IVertexAndEdgeListGraph<TVertex,TEdge> g= ...;

  var graphviz = new GraphvizAlgorithm<TVertex,CustomEdge<int>>(g);
  graphviz.FormatVertex += OnFormatVertex;
  graphviz.FormatEdge += OnFormatEdge;

  var output = graphviz.Generate(new FileDotEngine(), "graph");  
}

public virtual void OnFormatEdge(object obj, 
  FormatEdgeEventArgs<TVertex, CustomEdge<int>> e)
{ 
  e.EdgeFormatter.Label.Value = e.Edge.Id.ToString();
  e.EdgeFormatter.StrokeColor = Color.Blue;
}
...

Custom Edge class:

public CustomEdge : Edge<TVertex>
{
   public int Id {get; set;}
}

.Graphml Way

Some class:

...
public ExportGraphml()
{
  var g = new BidirectionalGraph<int, CustomEdge<int>>();
  ...
  using(var xwriter = XmlWriter.Create(...))
    g.SerializeToGraphML<int, CustomEdge<int>>(xwriter);
}

Custom Edge class:

public CustomEdge : Edge<TVertex>
{
   [XmlAttribute("id")]
   public int Id {get; set;}

   public virtual string ToLabel()
   {
      return Id.ToString();
   }
}