This is a test of religious faith, are you willing to believe something that is in direct conflict with reality?
Believe the apple is blue and your world of religious dogma and sense of well being persists unabated.
Believe your lying eyes that the apple is red and your world of religious dogma starts to crumble, creating internal conflicts and emotional anguish.
The religious cult you have been associated with since you were a child, your friends and family, believe the apple is blue.
Who are you to question it?
Take the path of least resistance, deny reality.