> <i>Similarly, that you can change the appearance of something’s color is not the same as changing its color. You can make an apple look green or blue, but that is not evidence that the apple is not red.</i><p>But the apple is only "red" when illuminated by "white" light, that closely matches the color of our sun. Its redness is a property assigned to it by our brains. There is an objective property that it has - which is the frequencies of photons that are reflected, instead of absorbed - but I would argue that that is not color.<p>> <i>For example, you may wonder whether unobservable entities such as electrons and electromagnetic fields really exist.</i><p>I don't think those two things are "unobservable". We clearly <i>can</i> observe them, based on how they effect things around them.<p>The alternative - which is acceptable, I guess, philosophically - is that we can't observe <i>anything</i> except the firing of the neurons in our brains.