// This one is used by default
// Groups are set based on the Prefixes
function default_coloring(d) {
  return color(d.group); 
}

// This function will group nodes based on the
// Rgular expressions you've provided
function regex_based_coloring(d) {
  var className = d.name
  
  var rules = ["Magical", "Mapp", "^NS", "^UI",  "^NI", "AF", ""];
//   var rules = ["ViewController", "View"]
  
  for (var i = 0; i < rules.length; i++) {
    var re = new RegExp(rules[i], "");
    if (className.match(re)) {
      return color(i + 1)
    }
  }
  return "black";
}

// Filling out with default coloring
node.style("fill", default_coloring)
// node.style("fill", regex_based_coloring)
  
force.start()