If you use a device with support for Android Auto, then you might want to check and see if Google's new UI changes have appeared for your interface. As reported by the folks over at 9to5Google, new Material You accent colors have started to show up in the latest updates for Android Auto users.
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These changes come with Android Auto version 13.4. There's not a lot of changes under the hood, although the new Material You theme additions do add a bit of variety to the software interface, similar to what we're seeing on Google Pixel smartphones. Some screenshots below from the 9to5Google team show accent colors on some UI elements including the Settings menu and notifications.
While the Android Auto colors are designed to match the rest of your device's UI, there are some inconsistencies which seem to indicate that the new update isn't the final version. In any case, we're bound to see more refinements in future Android Auto updates.