Anybody who's taken psychedelic drugs has likely seen this color already. Overlapping sensitivity of the cone cells doesn't matter when the image is generated without light. Psychedelic visuals are full of impossibly saturated colors.
You can also approximate this effect by tiring out some of the cone cells by staring at a bright area of saturated color, then looking at a different color. See:
https://en.wikipedia.org/wiki/Impossible_color#Chimerical_co...
I was going to suggest perhaps auras — people who see these (associated with migraines).