THin blue line flashing to outline text etc..?
Goto the SETTINGS, then GENERAL, then ACCESSIBILITY, then SWITCH CONTROL. Reset the switch to OFF .
THis has solved the problem for me twice. For no reason, my iPad has twice flipped this switch ON, with the sudden appearance of flashing blue outlines. As this seems to happen after 12 months, it's no big deal to live with, as the solution is painless and free!