OCD becomes worse over time if not treated. I'm not referring to anyone in particular, but once a person with this tendency notices something, they can become overly fixated. If gour screen didn't bother you until you read this thread, rotate the tablet until you don't know which way it's oriented. If you think you see the yellow area, but see it on the right, you're looking too hard. Viewing angle also affects screen color and brightness. I did the rotation thing a few times, and was wrong about which side I thought was yellow 9 times out of 10.
If you have a shadowy line, return it.
I have some mild OCD, took me a while to convince myself I wasn't just seeing things.