Hi.
LCD screens have pixels which are made up of 3 sub-pixels of red, green, and blue. It is possible that one green sub-pixel may be stuck in the 'on' position. A quick internet search for the term 'stuck pixel' will reveal that this is a fairly common situation for LCD screens, not just those from Apple.
Now, one potential way to attempt to un-stick a stuck pixel is to use an application that activates all of the pixels on the scree at the same time, and can change the colors through the 3 primary ones of red, green, and blue, as well as all of them (white) and none of them (black). The free 'flashlight' app will activate all of the screens pixels, and you can set it to automatically 'strobe' through multiple colors of your choosing. So you may be able to use this app to 'shock' your screen pixel and un-stick it. It may or may not help, but it will only cost you a little bit of your time (and no money) to try it.
Message was edited by: jal741
