I have this problem in similar fashion. One day, the screen just went to a wall of lines and colors. It was a solid wall, meaning there was no image behind a transparent wall of lines like the graphics problem people are having these days.
I could reboot it only sometimes, meaning it would labor to start and sometimes only get the deep blue screen. Sometimes it would bong once, cycle and start. Sometimes it would bong, cycle for a long time and then turn off. And after about a dozen times getting by like that, it would either not turn on all or it would bong and just turn off.
That was months ago and I decided to search again to see if there might be a solution because the Ubuntu Dell I'm using is lacking in features.
Though the following link is from 2006 (for the 2006 models) and mine is a MBP Model ID 8.2 (which is from 2011/2012) it worked (or so I think, because I'm using it again after many months but I have not tried to reboot to see if the fix has taken):
Quote: "You can get your computer to restart by holding down cmd-opt-p-r after turning on the power. Keep the keys pressed until you hear two 'bongs'."
https://discussions.apple.com/thread/590...
Disclaimer: For me, it didn't go quite according to those instructions. I hit the keys after the gray screen came on before the bong. It went BONG, cycle, black, gray, BONG, cycle, black, gray... So I let go of the keys. It turned the deep blue. I watched for a moment and saw my cursor. I waited, then hit the key combo again and it went: gray, BONG, cycle.... SPLASH SCREEN! YAY! And after many months, it's working again.
In the meantime, I'm saving all my data to an external drive (like I didn't do foolishly before) before I try rebooting.
ps. I suspect I'm having a heat issue. I used the mac on my bed all the time (as a norm for years) leaving it on all the time. The battery has swelled, too, putting pressure under the touchpad causing "left click" not to work without smashing down hard (which is not a good idea). I read here to get a new battery (if that's your issue, too):
http://www.everymac.com/systems/apple/ma...
There's a link in body of the text leading to a page telling you how to do it yourself.
Sadly thats not a good sign. Did you get your system wet at some point? Sitting it down in a puddle or spilling something on the keyboard?
Given the system is on the newer side do you still have AppleCare (extended care)? Or have an Apple Store near you?
Are you up to fixing your system your self? Do you have the needed tools and skills?
by Dan