Here is a gvpr (http://www.graphviz.org/pdf/gvpr.1.pdf) program that takes a standard Graphviz input file and outputs the starting node in yellow, children (and edges) in green and other nodes and edges in lightgrey.
BEGIN{
node_t aNode, Start;
graph_t aGraph, Root;
int seenE[], seenN[];
int Ecnt=0;
string start;
/////////////////////////////////////////////////////////////////////
// the anEdge argument is just for bookkeeping
// each call creates a new instance
// so the nxtedge call does not over-write
void nodeTraverse(node_t thisNode, edge_t anEdge){
print("// NODE: ", thisNode.name, " seen: ", seenN[thisNode]);
if (seenN[thisNode]!=1){
seenN[thisNode]=1;
thisNode.fillcolor="green";
thisNode.style="filled";
for (anEdge = fstout(thisNode); anEdge; anEdge = nxtout(anEdge)){
print("// edge: ", anEdge.name, " ", anEdge.tail, " ", anEdge.head, " seen: ", seenE[anEdge]);
if (seenE[anEdge]==0){
anEdge.color="green";
seenE[anEdge]=1;
print("// recurse: ", anEdge.head);
nodeTraverse(anEdge.head, anEdge);
}
}
}
print ("// DONE: ", thisNode.name);
} // end of nodeTraverse
//////////////////////////////////////////////
}
BEG_G{
Root=$G;
start=ARGV[0];
print ("// start: ", start);
Start=isNode($G, start);
if (Start==NULL){
printf(2, "Error: unknown node >%s<\n", start);
Ecnt++;
}
if (Ecnt>0) exit(9);
}
//
// grey out all nodes & edges
// we will color the ones we want later
//
N{
$.style="filled";
$.fillcolor="lightgrey";
}
E{
$.color="lightgrey";
}
// now find all the children & color them & their edges
END_G{
nodeTraverse(Start); // no edge parameter on this call
// Start=isNode($G, start);
print("// Start: ", Start.name,Start.color);
Start.fillcolor="yellow";
}
The (Linux) command line is something like this. Note the -a estimator piece of the command that specifies the starting node
f=colorChildren0.gv;T=png;F=`basename -s .gv $f`; gvpr -c -a estimator -f colorChildren2.gvpr $f | dot -T$T >$F.$T
The above command produced this:
