Notification Icon with the new Firebase Cloud Messaging system

Unfortunately this was a limitation of Firebase Notifications in SDK 9.0.0-9.6.1. When the app is in the background the launcher icon is use from the manifest (with the requisite Android tinting) for messages sent from the console.

With SDK 9.8.0 however, you can override the default! In your AndroidManifest.xml you can set the following fields to customise the icon and color:

<meta-data
        android:name="com.google.firebase.messaging.default_notification_icon"
        android:resource="@drawable/notification_icon" />
<meta-data android:name="com.google.firebase.messaging.default_notification_color"
        android:resource="@color/google_blue" />

Note that if the app is in the foreground (or a data message is sent) you can completely use your own logic to customise the display. You can also always customise the icon if sending the message from the HTTP/XMPP APIs.

Use a server implementation to send messages to your client and use data type of messages rather than notification type of messages.

This will help you get a callback to onMessageReceived irrespective if your app is in background or foreground and you can generate your custom notification then