For the graders to do this in the most simple way possible, they need to always have a true mass produced, second printing on-hand (which were all manufactured with the same colored cover). Just about anyone who isn’t colorblind would be able to tell the difference under the same lighting. In fact, I don’t think anyone who’s willing to spend big money on the true Blue cover has ever been fooled by the CGC label. Additionally, all the eBay sellers I’ve come across either know the difference or change their descriptions/pricing when notified about the error.
Unfortunately, the only people who haven't learned how to distinguish between the two second print covers are the CGC graders, but this can easily be fixed if they’re willing to do so