AFAIK, the appearance of the visual alert is up to the station or cable system. They can make it as pretty or as plain as they want so long as the necessary information is there.
What bothers me is that my cable company’s system turns off every channel completely, including the news channels that usually have more and better information. It shuts off a live person and a radar map during a tornado warning in order to scroll the text of the warning with a computer-generated voiceover. :rolleyes:
ETA: And what’s worse is that there’s absolutely nothing on HD channels. If you’re watching DeathWatch '12 on the NBC affiliate in HD, the picture freezes and you get nothing unless you know that you have to turn to an SD channel to get the scrolling text with the voiceover from the machine. And you can’t get the more substantial information until about 60 seconds after the robot finishes talking, when the cable system switches the channels back on. For that minute, you get whatever is playing on the radio station that acts as the EAS entry point for the area.