MacBook Pro Freezes & Vertical Lines Appear

Hi!

I own a MacBook Pro and starting today, it would freeze, the screen would turn peach with gray lines. The first time it happened was a few hours ago, and then now. I don't know if this is something I should be hugely concerned about. It is noteworthy that it had completely crashed in December 2014, and I actually had a new Hard Drive put in. Prior to that my MacBook Pro was working very fine.

As for troubleshooting, I put it in Single User Mode and when the command line prompt appeared, I typed in Fsck - fy. I did this 2 times until the prompt said ok. That didnt work. The second thing I did was reset the NVRAM/PRAM. And that has worked both times. I don't think it's something I should be doing over and over again. I worry I will have to. (All this techie things I had to google, I am way out of my element and would appreciate any help).

This is what it looks like before it freezes, or shuts down.

Details About my MacBook Pro

-Purchased in 2011

-Processor 2.2 GHz Intel Core i7

-Memory 4 GB 1333 MHz DDR3

-Graphics Intel HD Graphics 3000 384 MB

Software OS X 10.9.5 (13F1507)

If anyone has had a similar experience or maybe knows what may be causing this, I would really really appreciate some feedback.

Sincerely,

Mariane