I have a vertical white bar running down the middle of my screen. I have seen it before, but it has disappeared within a few minutes. Now it won't go away even after turning off the tv and letting it sit.

You just contact any service technician.
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Check and replace damaged components; or, check for any loose solder terminal/s at its vertical scan output section circuit. Gopakumar Gopalan Google

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Line faults & possible causes to LCD & Plasma screen are given with illustrations. You can get an idea about the fault to an extent. Faults to all LCD & Plasma screen are similar, irrespective of its brand and screen size.

my colour is green why?

Well if this is a tube type, it can be attributed to vertical section. Cold solder on vertical IC, the vertical gone bad or some components on the vertical is at fault.

If your not on electronics better to have it check by a repairer.

Hope this helps.

Don't let the kids near the TV.

the adjustment box for colour, brightness and contrast stays fixed on the screen. i tried pressing the exit button.... after a few times it disappears only to reappear within a few minutes. also the auto adjustment option, for which we are supposed to manually press the i button, keeps auto adjusting the screen whenever it feels like it. the box appears right in middle of the screen and is a real nuisance as it blocks out the main portion.

On a non H.Def plasma, there is a PCB that runs along the bottom of the screen that is attached to the screen by a several brown/gold colored flat ribbon cables. I've seen where this ribbon cable is not seated properly in the jack. The ribbon cables are generally responsible for that section of the screen. Next possibility is the PCB itself is defective.
Not to scare you, but the plasma screen itself is a possible suspect.

I had a smililar problem after taking it apart i realised that i had screwed my mount skrews into the video main board and cracked it along with a few soldered wires, if you havent done any physical dammage to it try a firmware upgrade

You'll have to locate the vertical output IC which should be mounted onto a heatsink, then take out a good magnifier under the printed circuit board and examine the solder connections on the pins of that IC and resolder the ones that are cracked.