I haven't read it for a while, but Dennett made a case in 'Consciousness
Explained' that red is not a physical phenomenon but merely a tag which
we attach to certain stimuli. This seems to match my own experiences; I
remember an optics lecture at school where the lecturer shone a light on
a board of colored squares, and the center square was red. Only when he
switched off the light did we realise that he was shining a non-red light
on a non-red square, and there wasn't a single photon of 'red light'
reaching our eyes. So something else had confused our brains into
sticking a 'red' tag on that square, even though it had received no
supporting data from the retina.
Most people seem to believe that they know how their brains work, but
most people haven't seen what happens when their brains go wrong, which
is where the real data on brain operation lies.
Mark