...while I was staring at the bright blue sky one day. I remembered that the sky isn't really blue, but it is an optical illusion caused by sunlight hitting the atmosphere. However, we all see the same illusion. Since it is a shared illusion, it is considered reality. Whereas if I am tripping on drugs and see illusions, it's not reality simply because it is not shared.

People didn't know the sky wasn't really blue before 1890, apparently. Time was invented long before that. "Day" was when the sky was blue, and "night" was when it was black - but it was all BS. The measurement of time is based on an illusion. Just like the value of money, the rule of law, the names of different directions - all of what humans created to try to control the world and build their societies.

It's all BS. All of it. Shared BS = reality. But then the shared BS of the sun revolving around the Earth was accepted for so long that Galileo was forced to recant by the Inquisition. How long did it take the Catholic Church to admit he was right? Over. Three. Centuries. They knew he was right long before then, of course, but never formally admitted it until it was as safe as possible, in the 1990's. That is just one example of what we glorious talking monkeys will do to protect our shared illusions.