And what, for example, about a water mirage in the desert? Should we say that's not an illusion, on the basis that your brain IS accurately receiving the actual visual information that is travelling from the scene to your receptors?
Living things survive. The best explanation of how that is accomplished is by doing and acting more in accordance with the world that it's competition and predators. Now that leads to the conclusion that the best representation of the world is the most accurate one of the world. We are about four billion years down that path.
This thing about red being an illusion just make my blood boil. If sense information is reliably cataloged it seems fair for those who do so to be able to label what they see using consistent code. A code that matching physical dimension and object appearance in the real world.
Optical phenomena can lead to representations from great distances away has been demonstrated over and over. So mirage and other object illusions can be as the human sensing them sees them. The illusion is not that there is this image but that the image is nearby. I can go on like this all the time you have. My view is one where normal processing of normal information leads to wrong interpretations result in reports of illusions.
distorted sensation by drug or fatigue has medical cause to misrepresented by the afflicted subject and that is a valid illusory state.
Sunlight and sodium light have different properties so the red and blue cars are actually what the observer received from her receptors. And that is just coding of information received as experience, not illusion at all.
We need to put illusion where it belongs. If sense are working properly and conditions are normal then what is seen, heard, etc. is perceived as very near what is received by sense. If we call changing external conditions sufficient to get two different sense reports that is definitely not illusion worthy. It is only when the unexpected is seen and improperly reported like when conditions result is far away images to be seen nearby or rods are improperly seen swinging through window the window that is built as if it were short one one side and long on the other and the rod is just oscillating in one pane are actually just oscillating within a as the window that we are talking illusion. The illusion is explained by fooling the processors to take what is seen and complete it as if it were a window rotating and a rod following suit leaving just the little detail of the rod appearing to pass through the window as evidence the observer and his tools are being fooled.
Clearly modern philosophers who claim red is an illusion is leading from the the presumptive error that what is there must be reported as essence to be a translation of reality as was the case before science really got in the game. Now we know that senses pretty faithfully reflect the nature of the world to the organism and that the organism has methods to represent these actualities in such as image and oral code on a more or less one to one basis.