It is interesting to me that if there would be a way to stimulate red and blue cones, without stimulating green, you would see a color never seen before. As there is no wavelength that accomplishes that.
You've heard of super-tasters? There's a genetic variation that creates a kind of fourth color receptor in some people, apparently giving them the ability to perceive colors others can't!
> One study suggested that 2–3% of the world's women might have the type of fourth cone whose sensitivity peak is between the standard red and green cones, giving, theoretically, a significant increase in color differentiation.
