use supports-color module

To check if colors should be used or not.

It allows you to force colors through the use of command line flags.

See https://github.com/sindresorhus/supports-color/blob/2ae39320b7ca26c2803b4da531ed9bbcc40d78a3/index.js#L11

lib/report/common/defaults.js

@@ -4,6 +4,7 @@
  */
 
 var Report  = require('../index');
+var supportsColor = require('supports-color');
 
 module.exports = {
     watermarks: function () {
@@ -23,7 +24,7 @@ module.exports = {
 
     colorize: function (str, clazz) {
         /* istanbul ignore if: untestable in batch mode */
-        if (process.stdout.isTTY) {
+        if (supportsColor) {
             switch (clazz) {
                 case 'low' : str = '\033[91m' + str + '\033[0m'; break;
                 case 'medium': str = '\033[93m' + str + '\033[0m'; break;

package.json

@@ -70,6 +70,7 @@
         "fileset": "0.1.x",
         "which": "1.0.x",
         "async": "0.9.x",
+        "supports-color": "1.2.x",
         "abbrev": "1.0.x",
         "wordwrap": "0.0.x",
         "resolve": "0.7.x",