Had this problem with my mid 2010 15” MacBook Pro6,2. Read the solutions here and found that when i pressed on certain spots the lines disappeared. When i removed the bottom of the case, i poked around and found the pressure point where the lines would vanish. Instead of using a penny or a ball of tape, i opted to use 2 CORN CUSHIONS! I simply stuck them to the trouble spot and put the bottom back on. This put enough pressure on the spot to keep the pink lines at bay! Hope this helps!