Spoiler alert: There is no support for it yet. But it is defined in the Media Queries Level 5 spec that includes other recent, but more familiar user preference features, like
The Polypane blog goes into …
Favicons are the little icons you see in your browser tab. They help you understand which site is which when you’re scanning through your browser’s bookmarks and open tabs. They’re a neat part of internet history that are capable of …
:hoverstate but you don't leave the page then, on a mobile device, there is a chance that
:hoverstate "sticks." You'll see this with stuff like jump-links used as tabs or buttons that trigger on-page functionality.