title: how to change the active footertab background color in nativebase
body: <p>I want to change the background color of my active footer tab in native base. I haven't found anything on that o the official doc. Pls, guide me on this. Thanks</p>
  
  <pre><code>&lt;Footer style={styles.footer}&gt;
      &lt;FooterTab  style={styles.footerTab} &gt;
        &lt;TouchableOpacity
  
          onPress={() =&gt; this.props.navigation.navigate('Mainhome')}&gt;
          &lt;Image
            source={require('../assets/home.png')}
            style={styles.footerIcon}
          /&gt;
        &lt;/TouchableOpacity&gt;
  
        &lt;TouchableOpacity
  
          onPress={() =&gt; this.props.navigation.navigate('Search')}&gt;
          &lt;Image
            source={require('../assets/search.png')}
            style={styles.footerIcon}
          /&gt;
        &lt;/TouchableOpacity&gt;
        &lt;TouchableOpacity
  &lt;/FooterTab&gt;
  &lt;Footer&gt;
  </code></pre>