There are always variations in vibrancy, contrast, saturation, etc., in all LCDs, even those from the same product line from the same manufacturer, even using same panel vendor.
Even if you got 50 people who think they're screen is perfect to post photos (which you won't), you would not get 50 identical photos, and even if you did, there's no guarantee that your replacement iPad would have a screen identical to what you've seen in the photos.
Every attempt at determining the probability of a perfect screen, based on photos, store location, serial number, date of manufacture, etc., has failed miserably in predicting what another person's screen will look like.
Don't waste your time or energy playing screen detective. The ONLY way to get an acceptable one, if one even exists, is to buy/exchange/return iPad after iPad, until you get one that looks good to YOU.