public int getColor(Vertex v) {
		try {
			return vertexColor.getValue(v);
		}
		catch (NoValueException exc) {
			return white;
		}
	}
Whitens the children of v.  It is only called after v has no more
 children left and we have backtracked to the calling parent of
 v.  This is to ensure that we don't miss out on any paths that
 contain a child of v which has other parents.
Ghidra/Framework/Generic/src/main/java/ghidra/util/graph/Dominator.java