How can I change the color of MediaSessionService's notification when the currently playing MediaItem doesn't have an artwork ?

Android 14 One UI version 6.1

I am working on a local music player app using a MediaSessionService.

Obviously, most audio files do not possess an artwork. So, what defines MediaSessionService's notification's color palette when the current MediaItem doesn't have an artwork ?

After a quick test, it seems as if the notification's color palette depends on the app's icon. Here's an example with a generic red icon:

However, I would like to set a custom color palette for the notification which doesn't depend on the icon's color. Can it be done and, if so, how?

At first, I thought the solution was to use MediaNotification.Provider as specified in the documentation. However, the documentation also specifies this:

Note: Starting with API 33 the System UI notification is populated from the data in the session. Accordingly, customizations of the MediaNotification.Provider have effect before API 33 only.

Which means that it has basically no effect starting from Android 13.

Also, as a slight deviation from my main question, the two custom buttons' icons (thumbs up and down) are white despite the fact that their vector assets are colored. In fact, using these same drawables in an activity displays the desired colors. Is this working as intended ?