If color is a behaviour of the brain, then why are people who are color blind still able to see the sky? If it is indeed simply the reaction of our brains to moving electrons, why don't coloblind people have a blank space where things with those colors are?
Our receptors are divided into spatial and light sensitive receptors. If color is objective, then shapes are as well. A blunt object would cut one person, but bounce of another. Balls only roll because we percieve them to roll.
Now does that make sense?
Actually, something like this can happen. The best way to demonstrate this is to get out some black and white film and take some pictures with a red filter over the lens. That would simulate blue-blindness (although human blue-blindness is not exactly equivalent).I had a college professor with a blue deficiency. He said he could see blue in sunlight, but in dimmer light, blue objects looked black. Since he could see and understand blue, he could describe the perceived difference.
All objects in the real world have complex spectral distributions. Nothing in real life emits or reflects a single wavelength. There are an infinite number of possible mixtures of spectral colors that can give the subject impression of green (or any specified shade).