Google has confirmed that Material You is set to grow beyond the bounds of the Pixel family, but that doesn’t mean it’s done evolving and growing in new ways. An experiment in Android 12 Beta 3 expands the reach of the dynamic theming system to home screen icons, but only for Google's own apps. Now with Android 13, third-party apps are free to create their own theming-friendly icons so you can have the two-tone icon packs you’ve always wanted without installing a custom launcher.
Like all of the other ways an app can be styled by Material You, themed app icons take on the tint of your wallpaper. Depending on whether you’re currently in light or dark mode, this will either style the background of the icon or the icon itself.
Themed icons are an opt-in feature, so this won’t be forced on anybody that isn’t a fan of the aesthetic. If you want to turn on the dynamically themed icons, simply long-press a blank spot on the home screen, choose Wallpaper & style, then scroll down to find the Themed icons toggle.
Google is urging app developers to add support for themed icons. The requirements are fairly simple, requiring a new monochromatic vector icon — probably just a mask of the original app icon or reusing a notification icon — and a couple tiny changes to the launcher's adaptive icon XML and the app manifest.
As of the first developer preview, there's no automated re-styling of app icons, and there's currently no indication that there ever will be. As a result, apps without support for themed icons show up in full color and break the aesthetic. Of course, this is only the first developer preview and the only apps with themed icon support belong to Google, at least until the Play Store allows apps targeting the Tirimasu SDK.
Plenty of apps will surely make the necessary changes in time, but it's unlikely that every app developer will make this a high priority, particularly developers that wait a long time between updates or avoid raising the target SDK for one reason or another. In the meantime, you'll probably either want to leave themed icons turned off, or go to the trouble of keeping non-themed icons out of your home screen.