I was using my 2011 27 inch i7 Imac and the screen suddenly went green! And i had to shut it off with the power button. And now it doesn't boot up anymore! It will start up and display pink bars and start to load but then it will get stuck and then restart. And it will do this until you turn it off. Originally i thought it was a bad GPU. I ran the Apple Hardware test and it threw a 4MOT/4/40000003 HHD-1551 code which simply says that the hard drive fan has gone bad and that has nothing to do with the symptoms my Mac is experiencing. I read some forums about this issue and there was mixed opinions about the issue. Any help is appreciated.