title: Set a custom background color to the button
body: <p>What is the correct way to change the color of a button ?
  My button :</p>
  
  <pre><code>&lt;button id="easy_mode" href="#gameZone" class="btn waves-effect waves-light spacing theme-color" &gt;
  </code></pre>
  
  <p>Theme color:</p>
  
  <pre><code>.theme-color {
      background-color: #ee6e73;
  }
  
  .theme-color:hover {
      background-color: #F18B8F;
  }
  </code></pre>
  
  <p>the button loses the color after it has been clicked. What am i missing ?</p>