Posted: Feb 28, 2016 9:12 pm
romansh wrote:
I have a problem of thinking of the double decker bus as red in some sort of absolute way, never mind the hint of radio.
A lot of humans have imaginary problems. A surprising number of them try to insist that these imaginary problems are philosophically important.
The bus, being covered by pigments which absorb all of the visible spectrum but red, appears to be red. You tried to make things tricky with an example of additive color with the yellow which was composed of red and green frequencies of light. But that example doesn't even apply to a bus, unless the bus appears red because it's red-hot, in which you've got bigger problems than the color of the bus. Additive and subtractive colors represent different sets of rules. Additive colors only occur when a surface is emitting light. Until very, very recently in our evolutionary history, most surfaces didn't do that sort of thing unless something imminently lethal was about to happen. So additive color isn't going to help us understand how color perception works in a way which is relevent to your red bus. There isn't a reflecting/refracting surface when you're dealing with additive colors, not in the same way as there is with a red bus. Or a red apple. Or a robin's questionably red breast (I always felt it was more a brownish-orange).
I think one thing which would really help the conversation is if we try not to flip back and forth between additive and subtractive colors or treat them as if they were equivalently important from the perspective of color perception as an evolved trait. Additive colors are a really great example of things we didn't evolve to deal with very much. Just like my earlier example with temperature perception and most naturally occurring temperatures of things being more homogeneous than what stimulates the erroneous response. I'm glad additive colors work for us the way they do, because color computer monitors, television screens, pointalist paintings, and projected movies are quite enjoyable, but they're a very large range of examples of tremendously useful illusions, really, when compared to the subtractive colors we perceive everywhere else.