I have been using HTC One X for over a week now. When I got it first, I noticed the yellow spot right away on left bottom corner. It was specially visible in White/grey background.
I found a pressure point just beside the yellow spot. When I gently pushed that area with tip of my nail the yellow spot would disappear. Although it would come right back when I release the pressure.
I kept doing it for days and guess what now yellow spot is almost gone...maybe 5% left or maybe its just me now
Let me know if this works for any one. Good luck