Let’s go step by step.
A bunch of pictures were selected for the test.
An excellent photo to reveal color shifting. Your monitor has to be set properly before you use this picture for a test. It’s sometimes difficult to judge what actually should be visible or not visible in a photo. The uniqueness of this picture is in the fact that we know from the author of this picture what exactly he did and wanted.
Can you see a black square in the left bottom corner?
It should not be visible. Set your monitor controls so that the black square is indistinguishable from the background.