How do you know if your perception on the world/your life is real?

oh yes I have considered it. i have also considered the fact that everything is different based on different perspectives. I have wondered if the color "red," for example, I see, is the same color "red" as somebody else sees. Or if a schizophrenic is labeled as having "delusions" when in fact it is the rest of us that do not have the capability of seeing what the schizoid is seeing. Nothing is concrete.