Kind of. The receptors are for short, medium, and long wavelengths.
Their ranges overlap a bit. Wavelengths that trigger the short receptors are translated as blue. The medium green, and short blue (at least as far as I can tell, depending on how you read the various descriptions), but as the receptors respond to the same light, the relative strengths of the signal (I think) are translated into the varying intermediate colors. Long (red) and medium (green) receptors firing at the same time are interpreted as yellow, for example. We can't "see" a reddish green, because red+green (long + medium) is already perceived as yellow. We *already* have a color that describes that combination.
We perceive colors that can be produced by the full range of physically possible overlapping wavelengths within the visible light spectrum. Take Magenta: there's no single wavelength that can trigger both the long and short receptors while NOT stimulating the middle receptors. But since they can be simultaneously stimulated by *separate* wavelengths, we have the "extraspectral" color Magenta - which you will not find in a rainbow, or in an illustration of the visible light spectrum. Wrapping a spectrum diagram around in a circle so the long red end overlaps with the short blue end is how we get a diagram - the color wheel - that shows all the colors we can see: all the possible combinations of length/receptor overlap that can be triggered by actual light sources.
Take a cup of hot water and mix it with cold, you get warm. We have a sensation mapped onto that combination of degrees of heat. Somehow these experiments are stimulating some kind of response where the brain isn't perceiving warm, its like the subjects are their hands in hot and cold at the same time. It doesn't make any sense physically, but the receptors are being stimulated that way nonetheless, and perceiving something new and completely imaginary, that is not mapped directly to anything in the real world. Or, I could be full of it.
Kind of. The receptors are for short, medium, and long wavelengths.
Their ranges overlap a bit. Wavelengths that trigger the short receptors are translated as blue. The medium green, and short blue (at least as far as I can tell, depending on how you read the various descriptions), but as the receptors respond to the same light, the relative strengths of the signal (I think) are translated into the varying intermediate colors. Long (red) and medium (green) receptors firing at the same time are interpreted as yellow, for example. We can't "see" a reddish green, because red+green (long + medium) is already perceived as yellow. We *already* have a color that describes that combination.
We perceive colors that can be produced by the full range of physically possible overlapping wavelengths within the visible light spectrum. Take Magenta: there's no single wavelength that can trigger both the long and short receptors while NOT stimulating the middle receptors. But since they can be simultaneously stimulated by *separate* wavelengths, we have the "extraspectral" color Magenta - which you will not find in a rainbow, or in an illustration of the visible light spectrum. Wrapping a spectrum diagram around in a circle so the long red end overlaps with the short blue end is how we get a diagram - the color wheel - that shows all the colors we can see: all the possible combinations of length/receptor overlap that can be triggered by actual light sources.
Take a cup of hot water and mix it with cold, you get warm. We have a sensation mapped onto that combination of degrees of heat. Somehow these experiments are stimulating some kind of response where the brain isn't perceiving warm, its like the subjects are their hands in hot and cold at the same time. It doesn't make any sense physically, but the receptors are being stimulated that way nonetheless, and perceiving something new and completely imaginary, that is not mapped directly to anything in the real world. Or, I could be full of it.