Cyan
“CYAN IS THE IMPOSTOR, I SAW HIM VENT!!!”
The colour cyan is remarkable for being absent from the real world. Seeing cyan is a symptom of being in an inverse world and/or Wyoming.
The cure for seeing cyan
There are many ways to cure seeing cyan. Some people claim that this is not really a disease, but who's going to listen to anybody who only plays Starcraft all nights. This is indeed bullshit, because the colour used in Starcraft is Teal, not Cyan. Some success has been claimed by psychotherapy and various related treatments, but the results have been inconclusive. The surest procedure for treatment is as follows.
Before you start, drink a can of beer. Save the can. This is important.
Remove the eyeball from its socket. Wash as usual. Then, make an incision with a razor blade, preferably near the optic nerve, unless you are going for the wifi method. Even then, don't cut the cornea. That may lead to blurry vision.
Pour the vitreous humour to the can. Hopefully you didn't drink the whole six-pack or you may be drunk enough to drink the humour too. If that happens, acquire more humour by some means.
Now, grab hold of the eyeball and carefully turn the eye inside out. You will need tweezers for this unless you have abnormally small hands or a large eyeball. Make the optic nerve to go out the incision, unless you're doing the wi-fi installation procedure for optic nerve ends instead.
Pour the vitreous humour back into the eyeball. You may need a funnel for this unless you have large eyeballs. If you run out of humour, just read some jokes from the Internet. It's not that serious. Sew the incision. Allow two weeks for recovery.
Note that this is nontrivial operation. That is why being drunk is recommended for ensuring a smooth operation.
In severe cases it may be necessary to turn the entire head inside out. This procedure is best left for trained surgeons. Ensure that they are properly drunk before the operation. The operation is not easy even for trained personnel.
