If you look real hard, there are some real differences throughout, some of the stays are welded, some are flattened, some have a s-seat stays some dont. the colour is similar, but again i wouldnt base the definitive answer on paint. Even looking at the dropouts, they are not exact now i have been able to find better pics, but is this again could be a model year change, or not.
Paint wise, they did go through a shocking point in Early 2000s, and not just with painted aluminium on Klein's either, it always felt if you looked at them too long the paint would disappear in front of your eyes. (look at the state of the factory paint below, especially around the drop out.- Although they are built to hit a price point, and whilst handwelded they are still mass produced production.
For me it will be the disc tab placement, and only then i would still only be 98%. if its on the seat stay its a blinking good knock off imho.