title: Android Material Design - How to change background color of Toolbar after CollapsingToolbarLayout is collapsed
body: <p>After the user scrolls down the screen, the image in the <strong>CollapsingToolbarLayout</strong> disappears and is left with a toolbar with the back button, content title, and settings menu. I want to know how to change the background color of that toolbar only when its in a 'collapsed' state.</p>
  
  <p>The action I am referring to is similar to this where the toolbar background color changes to green:</p>
  
  <p><img src="https://i.stack.imgur.com/7Nnvo.gif" alt="enter image description here"></p>
  
  <p>Below the CollapsingToolbarLayout I have a <strong>NestedScrollView</strong> with <strong>CardViews</strong></p>