[Boost-users] Creating custom depth first search visitor for Boost graph

I have a need to have a graph visitor algorithm similar to depth first search. The only difference is that if upon running discover_vertex the intended operation to be done on the vertex is not done I want the graph color value for this position to still be white. The reason is that the graph I am using the depth first search is a directed graph with no loops in it. A vertex might have two or more vertices providing information. If all the information is not there I want the visitor to try again. What do I have to do to gain access to the color map inside the visitor when I am in discover_vertex? Stephen