Screen goes green-ish or red-ish and flickers in ubuntu 14

I've been using ubuntu 10 for a while until I switched to ubuntu 14 (I formatted the computer instead or upgrading from 10 to 14). As soon as I started using the default Unity UI in ubuntu 14, my screen began to turn green-ish and sometimes red-ish (but mostly green). I thought the monitor was faulty so I changed it, but I noticed the same problem. So I thought the connections might be having problems and changed the wires that connect the monitor to the pc. Same thing happened. So I went back to the old monitor with the new wires. Same issue. Went back to my initial configuration of monitor+wire and I still experience the same.
It seems to happen at random times: the screen just gets a green tone (as if colors were really unbalanced) and flickers for a while back and forth (from regular colors to greenish). Then for a while it's normal and then suddenly it comes back.
Since I tried the hardware solutions I could think of, is there any software-related thing I could try?
Thanks.