Now that the Chromecast is truly coming into its own, Google can turn its attention to the little things. Specifically, the icon. The current cast icon design works fine for some apps, but not so well for others. The new guidelines are aimed at making the status of the icon easier to discern across a range of apps designs.
The old icon relied on a change in color to indicate connected/non-connected (see below). In some apps, it was more like a change in shading – far too subtle. The updated guidelines direct developers to use a solid fill in the screen portion of the icon to indicate a connection. With a few different color choices, developers get a ready-made icon set that will stand out well in almost any app.
The new assets will be available for devs in the next update to the Media Router Support Library, and there are new PSD templates for those using custom Cast icons. The new icon will probably show up in Google's apps first, but watch for other apps to be updated too.