title: Build fails with error: expected reference but got (raw string) #000000
body: <p>After upgrade to androidx and SDK 28 I get the following error when building my project:</p>
  <blockquote>
  <p>.../app/src/main/res/values/styles.xml:90:5-93:13: AAPT: error:
  expected reference but got (raw string) #000000.</p>
  </blockquote>
  <p>The relevant lines of values/styles.xml:</p>
  <pre><code>&lt;style name=&quot;menu_labels_style&quot;&gt;
      &lt;item name=&quot;android:background&quot;&gt;@drawable/fab_label_background&lt;/item&gt;
      &lt;item name=&quot;android:textColor&quot;&gt;@color/white&lt;/item&gt;
  &lt;/style&gt;
  </code></pre>
  <p>The fab_label_background resource (just in case) is:</p>
  <pre><code>&lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
  &lt;shape xmlns:android=&quot;http://schemas.android.com/apk/res/android&quot;&gt;
      &lt;solid android:color=&quot;@color/black_semi_transparent&quot;/&gt;
      &lt;padding
          android:left=&quot;16dp&quot;
          android:top=&quot;4dp&quot;
          android:right=&quot;16dp&quot;
          android:bottom=&quot;4dp&quot;/&gt;
      &lt;corners
          android:radius=&quot;2dp&quot;/&gt;
  &lt;/shape&gt;
  </code></pre>