My screen changes into neon colors by itself.i have replaced the scre.

Hi,

Was the phone dropped or did it get wet at all before the screen was replaced to try and fix the problem?

Try the following and check if any of them resolves the problem:

a). Wipe the cache partition and check if it now works OK.

b). Start the phone in safe mode and check if it works OK. If it does then a downloaded app is the cause of the problem. The trick is to find out which one. A downloaded app is one that you installed in the phone and was not pre-installed in the phone when you first got it.

c). Reset the phone back to its default operating condition to prove whether the problem is software or hardware related.

Be aware that a factory restore will erase all your data and downloaded apps.

If you decide to try this backup the phone to the cloud or a computer before performing the factory restore. Also if the phone has a Google account, ensure that you know the account user ID and password for the phone as you will need this to access the phone after it has been reset (FRP lock)

Backup the phone using the phone’s backup feature (found in Settings).

Once the phone has been backed up, reset the phone using the phone’s factory restore feature.

Once it has been reset:

If it still doesn’t work OK then there is a hardware problem. The phone would have to be opened and tested as to what is the cause. Here’s the ifixit Samsung Galaxy A51 guides that may help.

If it now works OK, using the backup that was made earlier, restore the phone to what it originally was by using the phone’s restore feature.

Once it has been restored, check that it still works OK