title: How to set group divider color for ExpandableListView
body: <p><img src="https://i.stack.imgur.com/85VXP.png" alt="enter image description here"></p>
  
  <p>I can set the devider color for the children using childDivider attribute (black in this example). But, I don't see any way to set the color of the divider between the collapsed groups. System seems to be showing a 1px white line.</p>