I've got the same problem... mostly. I get the pink lines on white, but not the green on black. My temporary solution is to use a small clamp to apply pressure to the casing just below the right speaker. Its a total kludge, but it solves the problem completely.
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This is on a 2010, 17" Macbook Pro.
Can anyone explain where the heat sink is that I can look at to try to address this and exactly what you do? Remove/reapply thermal paste to reduce pressure? Add something (a penny?) to apply pressure?