The psyche is a strange world of subjective wonders and horrors.
You may find yourself staring at a purple sky. Your friend standing right next to you staring at the exact same sky is saying, "It’s yellow, of course… can’t you SEE that it’s yellow?"
You’re looking at the obvious, extreme, unambiguous purpleness right in front of both of your faces and going…. "Huh??????"
If you can’t logically resolve the paradox between you, at last it comes down to the question of, "do you trust your friend or not?"
If you do, it is necessary for you to accept that your friend is truly seeing yellow.
Hopefully, said friend is equally willing to acceed that you are truly seeing purple.
If you continue to deny the supposition, you are no longer co- existing in any area of overlapping shared reality.