The colors on the screen are like limited to 8bit

The fact that the new user doesn't have the problem indicates that your original user account does have software that might be causing the problem. Safe Mode stops all 3rd party software from loading and only loads the minimal system files to operate. If the problem doesn't show in Safe Mode but does when you reboot normally that indicates you've got 3rd party software that is causing the problem. If that's the case running the free version of Etrecheck and posting the report according to this user tip, How to report the Etrecheck results using the Added Text feature, and we can see what might be causing the problem. It will be easier than migration all of your apps, settings and files from the old account to the new one.

Also, the Safe Mode boot might fix it as it does some repair as my previous post described.

That looks like a Display Contrast setting in that User Account.

Go to Apple > System Preferences > Accessibility > Display and make sure that the Contrast slider is set to Normal.

Give this a try: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.

Jacquesit wrote:

I did clear the NVRAM and the ruler for the display contrast filter did work again. Thanks, for helping.

This did the job.

Yea' your image was clearly showing a display contrast problem.

Many thanks to all of you.

You're welcome.

Just thinking out loud:

Old account:

• new account should have administrator priveleges
• enable iCloud for Photos, Files etc
• Logout of iCloud

New Account:

• login to iCloud
• Sync photos and files
• Check if everything is OK and manually restore other stuff
• delete old account

Safe mode clears some obscure caches, so it sometimes *can* fix things like this, just by running it.

It also prevents some programs from running which might interfere with things.

So why not migrate to the new user and delete the existing after done?