title: error: Error: No resource found that matches the given name: attr 'colorAccent'
body: <p>I'm learning Material Design, in particular I want to customize my app with Material Design also for the older Android versions. I'm reading this guide: <a href="https://developer.android.com/training/material/compatibility.html#SupportLib" rel="noreferrer">https://developer.android.com/training/material/compatibility.html#SupportLib</a></p>
  
  <p>About Color Palette, the guide says:</p>
  
  <blockquote>
    <p>To obtain material design styles and customize the color palette with the Android v7 Support Library, apply one of the Theme.AppCompat themes:</p>
  </blockquote>
  
  <pre><code>&lt;!-- extend one of the Theme.AppCompat themes --&gt;
  &lt;style name="Theme.MyTheme" parent="Theme.AppCompat.Light"&gt;
      &lt;!-- customize the color palette --&gt;
      &lt;item name="colorPrimary"&gt;@color/material_blue_500&lt;/item&gt;
      &lt;item name="colorPrimaryDark"&gt;@color/material_blue_700&lt;/item&gt;
      &lt;item name="colorAccent"&gt;@color/material_green_A200&lt;/item&gt;
  &lt;/style&gt;
  </code></pre>
  
  <p>When I try to run this code, I got this error:</p>
  
  <blockquote>
    <p>error: Error: No resource found that matches the given name: attr 'colorAccent'.</p>
  </blockquote>
  
  <p>...and the same error for colorPrimaryDark and colorPrimary!
  If I run this code into the values-v21/style.xml file, putting the " android: " tag before colorPrimary, colorPrimaryDark and colorAccent, as:</p>
  
  <pre><code>&lt;item name="android:colorPrimary"&gt;@color/material_blue_500&lt;/item&gt;
  &lt;item name="android:colorPrimaryDark"&gt;@color/material_blue_700&lt;/item&gt;
  &lt;item name="android:colorAccent"&gt;@color/material_green_A200&lt;/item&gt;
  </code></pre>
  
  <p>it works!</p>
  
  <p>So...I don't understand where I'm wrong :( I've surely updated the v7 support library</p>
  
  <p>Any help will be appreciated! :)</p>