I don't know how the settings were changed; my young daughter may have done it. Also, I just got the new update this morning. I have to touch, then double tap every time. Also, there is a yellow line around the screen and everthimg. I've checked all settings I know of, but I can't reverse this.
Sheryl found the answer herself. Quoting her comment:
If one has a similar effect (e.g. red borders shown), and it's not the accessibility settings, another place to look for is the development settings, which also has switches to highlight certain areas for "developer feedback" when testing an app.