InfoVis onBeforePlotNode method and changing nodes after rendering

Question

Im using the InfoVis javascript onBeforePlotNode method to set node colours.

onBeforePlotNode: function(node)
       {   
                if(node.data.mytype == "type1") 
               {
                   node.data.$color = '#d9d9d9'; //light grey
               } 
       }

What is best way to change node color after the visualisation has been rendered?

Ive tried

  sb.graph.nodes["mynode"].data["$color"] = "#fff";   
  sb.refresh();

but this will only work if the onBeforePlotNode is not used to set color

Any suggestions?