title: angular 5 matsnackbar change action button color
body: <p>I'm using MatSnackBar for my angular 5 project, and I cannot seem to change the color of the 'action' button. </p>
  
  <p>I've injected the snack bar to my HttpInterceptor:</p>
  
  <pre><code>    this.snackBar.open('Invalid Login', 'Ok', {
                      duration: 2000,
                      panelClass: ['my-snack-bar']
                  });
  </code></pre>
  
  <p>my css:</p>
  
  <pre><code>    .my-snack-bar {
          background-color: #E8EAF6;
          color: #3D5AFE;
      }
  </code></pre>
  
  <p>How can I change the 'Ok' action button color?</p>