I found that the edge coloring can be added in the TouchGraphConverter.java file.
The following function constructs the nodes.
public Node convertToTouchGraph(
Graph<V, E> graph,
TGPanel tgPanel,
boolean selfReferencesAllowed)
throws TGException
{
List<V> jgtNodes = new ArrayList<V>(graph.vertexSet());
Node [] tgNodes = new Node[jgtNodes.size()];
// add all the nodes...
for (int i = 0; i < jgtNodes.size(); i++) {
Node n;
if (jgtNodes.get(i) instanceof Node) {
// if our JGraphT object was a touchGraph node, add it unaltered
n = (Node) jgtNodes.get(i);
} else {
// create a TG Node with a "label" and "id" equals to the
// objects toString() value
n = new Node(jgtNodes.get(i).toString());
}
// store this for edge-related creation below
tgNodes[i] = n;
tgPanel.addNode(n);
tgNodes[i].setBackColor(Color.RED);
The last line, tgNodes[i].setBackColor(Color.RED) will make the node color to red in the generated graph.