From what I understand that might be Zebra at work
Zebra is a function of Magic Lantern which pops up blue ad red lines when your contrast is too high or too low in specific area of the picture. Do try and turn it off using the ML menu ( pressing the erase button ! )
If it still is there. then perhaps something is not right.. and maybe the devs can help you
EDIT: Ah ! pat you were faster than me, here !