While considering different forms of perception, I became interested in knowing how hallucinogenic drugs effect these forms. Do they effect solely the brain? Are your eyes accountable for the difference in colors and reality? So, I decided to research this. There are three types of hallucinogens: psychedelics, dissociatives, and deliriants. Doctors researching these have found chemical ingredients to be very similar structurally to the chemical seretonin in the brain. These hallucinogens interrupt the flow of natural chemicals across the synapses and cause different perceptual experiences. The act on serotonin synapses is initial and then expands to other parts of the brain according to the drug taken. Psychedelics change the way you perceive the world in an observational manner, turning off selective perception and allowing you to perceive everything around you. Dissociatives create sensory deprivation on the brain and your mind creates its own perceptions without any actual external stimuli. Diliriants produce completely false perceptions that aren't based on reality, for instance feelings of invincibility.
Here is a video of a fake perceptual LSD trip.
LSD is an example of a dissociate: