Updated the files.

my-app/node_modules/less/test/plugins/preprocess/index.js

@@ -0,0 +1,19 @@
+(function(exports) {
+    var preProcessor = function() {};
+
+    preProcessor.prototype = {
+        process : function (src, extra) {
+            var injected = '@color: red;\n';
+            var ignored = extra.imports.contentsIgnoredChars;
+            var fileInfo = extra.fileInfo;
+            ignored[fileInfo.filename] = ignored[fileInfo.filename] || 0;
+            ignored[fileInfo.filename] += injected.length;
+            return injected + src;
+        }
+    };
+
+    exports.install = function(less, pluginManager) {
+        pluginManager.addPreProcessor( new preProcessor() );
+    };
+
+})(typeof exports === 'undefined' ? this['preProcessorPlugin'] = {} : exports);