XamarinDevDays/Demos/app-myweather/MyWeather.Droid/Resources/values/style.xml

<?xml version="1.0" encoding="utf-8" ?>
<resources>
    <style name="MyTheme" parent="MyTheme.Base">
    </style>
    <style name="MyTheme.Base" parent="Theme.AppCompat.Light.NoActionBar">
        <item name="colorPrimary">@color/primary</item>
        <item name="colorPrimaryDark">@color/primaryDark</item>
        <item name="colorAccent">@color/accent</item>
        <item name="android:windowBackground">@color/window_background</item>
    </style>
</resources>