"The Colors Man, The Colors"

[Sandozboy]

That relatively famous line voiced by so many hippies during the '60s has me wondering about how certain drugs (especially "hallucinogens") alter and enhance a person's subjective view of colors and their hues.

Since the eyes are basically an extension of the brain, some cerebral cortex must surely be involved...could it be that it's all serotonin-induced? substances which trigger dopamine seemingly don't leave such an effect.

Any links to research on this matter is greatly appreciated.