My MacBook Pro is showing weird colorful rainbow lines on the display, and I can't see what I'm doing. The computer works fine; it is just the display that has a problem. I have already completely reset the computer and reinstalled the operating system per an Apple live chat, and it didn't work. I'm pretty sure it is something wrong with the logic board. Another weird thing is that when an HDMI or Thunderbolt cable gets plugged in and it sends the screen to something else, not only does it show up clearly on the monitor, it also shows up clearly on the regular mac screen! Another thing I discovered is that if I hold down the TAB button, the rainbow lines will always go away, but that doesn't work with other buttons.