Hi gooroopk. The grey app is the Automatic Classic app and accompanies Gen 1 & 2 adapters. The blue app is the new app and accompanies the Automatic Pro & Lite adapters. The apps will only work with their designated adapters. If you were formerly a Gen 1 or 2 user but have switched over to a Pro or Lite, once you set up your car with your same account, all your historical data for that car will transfer over to the new app and no longer appear in the Classic app.
To determine which adapter you have, please check this FAQ.