Why is my screen acting weird

Black is turning green - but not everywhere and not on screendump or on my ext. screen (photo taken with iPhone). If I press the unibody hard on the left side, then I can make the green disappear, but that's not a solution. This is a MacBook Pro (15”, mid-2010) 2.66GHz Intel Core i7 with 8GB 1067 MHz DDR3, an NVIDIA GeForce GT 330M 512 MB / Intel HD Graphics 288 Mb, and the OS is El Capitan v.10.11.6 To determine if the problem is caused by a graphics card or not, I would like to know if there is a way to have only one card/processor active at time?