Update On The Primary Colours

Already got a response to my primary colours question from T.J. Jankun-Kelly.

Some great points:

• "Perceptual spectral color space is three dimensional: two chromaticity
coordinates (which specify hue and saturation) and one brightness coordinate."
• "The space is not necessarily linear, but most approximations to it are."
• "Two spectral color combination, depending on the colors chosen and the weight of the combination, can give you a range of spectral colors along a line through the spectral color space (on the CIE diagram which the CIE space is embedded upon). You can actual get white light with a combination of only two colors if they are on opposite ends of the color space and space through the achromatic point (white)."

TJK also cited http://hyperphysics.phy-astr.gsu.edu/hbase/vision/colper.html which is a nice summary of colour science and makes a point that is key for me:

"It is found that many different combinations of light wavelengths can produce the same perception of color."

So there is a definite distinction between the dimensionality of colour perception and the actual space of light. I feel more confident now in asserting that the actual colour space of light is infinite dimensional but that it is projected onto a three dimensional non-linear space of perception.

So does that mean that the number of cones is the reason for the dimensionality of the (perceptual) colour space?

UPDATE (2004/06/08): TJK say yes. The number of cones is the reason for the dimensionality of the perceptual colour space. Chickens, which have 12 cones, would have a 12-dimensional perceptual colour space. Makes me think of a name one could use for an article on this topic: "If Munsell Were A Chicken".