sgApp/platforms/android/app/src/main/res/drawable/grid_background.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >
    <gradient
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:angle="90"
        android:centerX="0"
        android:centerY="0"
      android:startColor="#FF000000"
      android:endColor="#FF8E8E8E"
        android:type="linear" />
</shape>