diff --git a/app.js b/app.js
index 639c544..dc81d94 100644
--- a/app.js
+++ b/app.js
@@ -3,7 +3,8 @@ var app = new Vue({
   data: {
     attachRed: false,
     attachGreen: false,
-    attachBlue: true
+    attachBlue: true,
+    color: "green"
   },
   computed:{
     divClasses(){
diff --git a/index.html b/index.html
index 2dc2acc..7baf188 100644
--- a/index.html
+++ b/index.html
@@ -12,7 +12,9 @@
           :class="{red: attachRed}"
           ></div>
           <div class="demo" :class="divClasses"></div>
-          <div class="demo"></div>
+          <div class="demo" :class="[color, {red: attachRed}]"></div>
+          <hr>
+          <input type="text"  v-model="color">
     </div>
     <script src="app.js" charset="utf-8"></script>
   </body>