Well. You could alway get a pic of the inside? There was a change from 05 or 06 with the CD player outline being silver not grey. That would tell.
Or ask the original owner if he got a manual with the car?
But that can only be a import. They stopped making laser blue in 2006 here in South Africa and as Phil said. You cannot order a GTi in that colour. Look at this thread and the colour of doc's R32. They exact.
If you want to see if the file is shopped save it and compare the file to another file with the same resolution. Thats the easiest way to see if its Shopped. The one while will be much larger in size.
Here is the R32 thread:
http://www.golfgtiforum.co.uk/index.php?topic=38581.0Where is the Doc? I remember him hinting about getting another GTi. Surprised he didnt get a ED30?
Mike