When bright areas move quickly across a dark background, you occasionally see a greeny/yellowy blur behind it.

I understand the technical gubbins behind this, it's to do with the green elements taking longer to fade to black...

BUT can someone explain to me why, on a PAUSED picture when I move my eyes or head quickly side to side, i see the same effect..??

A Plasma never has a static picture - due to the way they work - a Plasma pixel can only be either ON or OFF, there's no possible brightness variation. In order to give an apparent variation each pixel is turned ON multiple times, usually on a 256 times cycle. So for half brightness you would flash the pixel ON only 128 times out of the 256, and accordingly for other degrees of brightness.

So your picture is actually flashing very fast - extremely clever things Plasma panels! (not to mention complicated).