Set Android Theme.Light for Alert Dialog

AlertDialog.Builder builder = new AlertDialog.Builder(
                    new ContextThemeWrapper(context, R.style.popup_theme));

<?xml version="1.0" encoding="utf-8"?>
<resources>
<color name="back_color">#ffffffff</color>
<style name="popup_theme" parent="@android:style/Theme.Light">
    <item name="android:windowBackground">@color/back_color</item>
    <item name="android:colorBackground">@color/back_color</item>
</style>

parent="android:style/Theme.Light"