Blue disks (I think they're more of a purple colour) for PS2 games aren't necessarily copied titles. Many early PS2 games came on them, since they're CD-ROMs instead of the silver DVD-ROMs that are more commonly used for PS2 games these days.
Unfortunately, the dreaded DRE (Disc Read Error) problem that afflicts millions of PS2s is most commonly a problem with blue disks, in that it may play silver ones fines, but in most cases the DRE problem will manifest itself with blue disks first.
If your PS2 is in warranty and this is indeed not a copied game, then get it replaced for a new model. If not, you can try using a DVD lens cleaner, but don't get your hopes up. Out of all the current-generation consoles, PS2's are easily the least reliable (even taking into account their greater installed user base). So you might simply be out of luck.