Dead pixel, dust or scratch?

I noticed what appears to be a dead pixel on my MBP after leaving it turned off for a few weeks. The thing is, when I look at it from different angles, it tends to fade away and disappear at certain angles. When I stare at it and move my head to look at it from different angles, it flashes between grey, pink, and at times green. Has anyone experienced this before? If so, is it a dead pixel, trapped dust particle/s or a scratch? The surface is smooth so I`m guessing it`s not a scratch or at least not on the outside of the screen.