how to change icon of notification using cordova-plugin-firebase?

I'm using cordova-plugin-firebase and I the icon appear good when the notification received in the header bar, but when I put the slide of the phone down to see the notification the icon appear different white square inside black circle. So any body know how I find this solution depending on the plugin itself, but I don't undestand it .

/res/native/android/res/values/styles.xml

<?xml version="1.0" encoding="utf-8" ?>
<resources>
    <!-- inherit from the holo theme -->
    <style name="AppTheme" parent="android:Theme.Light">
        <item name="android:windowDisablePreview">true</item>
    </style>
    <drawable name="notification_big">@mipmap/icon</drawable>
    <drawable name="notification_icon">@mipmap/icon</drawable>
</resources>

and /res/native/android/res/values-v21/styles.xml

<?xml version="1.0" encoding="utf-8" ?>
<resources>
    <!-- inherit from the material theme -->
    <style name="AppTheme" parent="android:Theme.Material">
        <item name="android:windowDisablePreview">true</item>
    </style>
    <drawable name="notification_big">@mipmap/icon</drawable>
    <drawable name="notification_icon">@drawable/ic_silhouette</drawable>
</resources>