[Galaxy S8/S8+]The screen color on the edge screen appears green and red

Your device is not faulty. The colors on the curved screen may look different
depending on your viewing position.

The slight green tint in color at the edges of the Galaxy S8/S8+ display that
you may observe on occasion is due to a phenomenon called WAD
(White Angular Dependency) which is due to the inclined curved surface
of the S8/S8+ edge screen.

For an AMOLED display, the WAD phenomenon results in the color white
sometimes appearing to have a Green tint, or on occasion a Blue or Yellow,
Red tint when viewing the AMOLED at an angle.

But when viewing directly from the front or side, the color will be as expected.