The orange box you see is ChromeVox's focus ring. This indicates where ChromeVox is currently focused.
There is not currently a way to turn this off.

I am going to change this bug into a feature request to provide a way to turn off the focus ring.

Please feel free to turn off ChromeVox (the screen reader application generating the focus ring) using this key combo:

ctrl + alt + z

You can also turn off this focus ring or others in Settings > Manage Accessibility Features

If you still have further issues, please send us a screenshot of the problem. 

Adding my personal opinion which differs from that of dsexton@: I feel that users should not be allowed to turn off the focus ring while using ChromeVox since it could add unneeded complexity to setup and learning.