code: function ChartColors () {
      var colorsLinker = function (scope, element, attrs, chartCtrl) {
          var pattern = attrs.colorPattern;
          if (pattern) {
              chartCtrl.addColorPatterns(pattern.split(","));
          }
  
          var thresholds = attrs.thresholds;
          if(thresholds){
              chartCtrl.addColorThresholds(thresholds.split(","));
          }
          
          if (attrs.colorFunction) {
              chartCtrl.addColorFunction(scope.colorFunction());
          }
      };
  
      return {
          "require": "^c3chart",
          "restrict": "E",
          "scope": {
              "colorFunction": "&"
          },
          "replace": true,
          "link": colorsLinker
      };
  }
docs: @ngdoc directive
  @name chartColors
  @description
  `chart-colors` is used to specify the colors to use in the chart. You can provide the colors or a function to determine the colors.
  
  Restrict To:
  Element
  
  Parent Element:
  c3chart
  
  @param {String} color-pattern A string containing comma separated hex colors
  @param {String} thresholds A string containing comma separated numeric values
  
  {@link http://c3js.org/reference.html#color-pattern| c3js docs}
  @param {Function} color-function Provide a function that receives the value to determine a color for that value.
  
  {@link http://c3js.org/reference.html#data-color| c3js docs}
  
  @example
  Usage:
  <chart-colors color-pattern="..." color-function="..." thresholds="..."/>
  
  Example:
  {@link http://jettro.github.io/c3-angular-directive/#examples}