[console.js] Use const instead of let

lib/logging/console.js

@@ -6,18 +6,15 @@ var websocket = null
 
 var logger = (function () { // eslint-disable-line no-unused-vars
   const sep = '\n/* ### NEXT TESTCASE ############################## */'
-
-  let color = {
+  const color = {
     red: '\u0033[1;31m',
     green: '\u0033[1;32m',
     clear: '\u0033[0m'
   }
   if (utils.platform.isWindows) {
-    color = {
-      red: '',
-      green: '',
-      clear: ''
-    }
+    color.red = ''
+    color.green = ''
+    color.clear = ''
   }
 
   function console (msg) {