Change background color of single specific menu items

I want to set the background color of all header items in a android menu within a navigation drawer. My layout looks like:

<menu xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:title="TopItem" android:id="@+id/top_item1"> // Here i want to set the background
    <menu>
      <group>
        <item android:id="@+id/sub_item1"
            android:title="SubItem" /> // Here no background
      </group>
    </menu>
  </item>
  <item android:title="TopItem" android:id="@+id/top_item2">
    <menu>
      <group>
       <item android:id="@+id/sub_item2"
            android:title="SubItem" />
        <item android:id="@+id/sub_item3"
            android:title="SubItem" />
       <item android:id="@+id/sub_item4"
            android:title="SubItem" />
      </group>
    </menu>
</menu>

Result should kinda look like:

I found out that i can set the text color by using something like:

MenuItem menuItem = navigationView.getMenu().findItem(R.id.menu_item);
SpannableString s = new SpannableString(menuItem.getTitle());
s.setSpan(new TextAppearanceSpan(this, R.style.TextAppearance), 0, s.length(), 0);

if (menuItem.getItemId()==R.id.nav_targets){            
  menuItem.setTitle(s); }

But how can i set the filling background color?

from Change background color of single specific menu items