MonoGame.Samples/StateObjectWindows/Platforms/Android/Resources/values/styles.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <style name="MainTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <item name="colorPrimary">#2196F3</item>
        <item name="colorPrimaryDark">#1976D2</item>
        <item name="colorAccent">#FF4081</item>
    </style>
</resources>