Can we see entirely new colors without being on drugs? This seems intriguing, somebody wants to try it out?

[...] and the colors flowed into each other in the brain's visual cortex, overriding the opponency mechanisms and producing not the color expected from mixing paints or from mixing lights on a screen, but new colors entirely, which are not in the CIE 1931 color space, either in its real part or in its imaginary parts. For red-and-green, some saw an even field of the new color; some saw a regular pattern of just-visible green dots and red dots; some saw islands of one color on a background of the other color. Some of the volunteers for the experiment reported that afterward, they could still imagine the new colors for a period of time.

https://www.science.org/doi/10.1126/science.221.4615.1078

https://en.wikipedia.org/wiki/Impossible_color

(thanks to astralcodexten)