I fail to see how messed up colours on an LCD have anything to do with a digitizer. Of course, stranger things can happen.

I believe the LCD connector is not seated properly. It may have loosened due to a (minor) fall after the customer left your shop or perhaps the connector was never properly secured to begin with. There is also some "grainyness" to the LCD image. This could be a connection issue as well.

When you get the device back, open it up and verify the connections (make sure to disconnect the battery!). If it still displays false colours, you may have a defective LCD. They are very sensitive and can fail if you handle them incorrectly.