JTL That is what Samsung wrote me:
"Thank you for contacting Samsung Technical Support.
I understand that you are experiencing issues with the display of the phone as it is straining your eyes. We are sorry to hear the problem you have encountered. I see that you want to downgrade the software update on the phone. I'll help you with the available information.
Once the phone is updated, there is no way to revert back the software on the phone. If you try to downgrade the phone to older version then it tends to rooting the phone. Samsung doesn’t recommend rooting the phone as it voids the warranty and the process is risky. Rooting bricks the phone and render it permanently inoperable.
Please do not root the phone, as rooting will be against the Samsung polices. Samsung will never consider or do service to a rooted phone. Adding to this, please do not trust any software that will advertise you on retrieving about the images on the phone they may be chances of fake websites/software."