We conventionally assume that an object's color is an inherent property of the object. Yet color is merely the wavelength of light reflected and its impact on our retinas. When white objects are placed under certain lighting conditions, for instance, their apparent color changes - and indeed, if their apparent color changes, doesn't their real color also change, since color is a perception? Isn't a white object under a red light actually, in that moment, a red object?

Let's agree that, at bottom, a thing's colour is a matter of how it affects us. Still, that rough thought can be sharpened in various ways. As a more careful second shot we might say: something is red if it is such that, in normal lighting, it will produce a certain visual response in normal perceivers. And for present purposes we can leave it open whether the response is best characterised in subjective terms (in terms of a certain look that red things typically have) or in neural terms (in terms of how our retinas and visual systems respond). For note that, either way, if we do analyse the notion of being red as a matter of being such as to produce a certain response in normal perceivers in normal lighting circumstances, it can continue to be such even when e.g. not in normal lighting.

Compare: the glass is still fragile even when it is dropped on a cushion and doesn't break, for being fragile is (roughly) a matter of being such as to tend to break when dropped on hard surfaces, etc. The rose is still a red rose, even though it looks a nasty murky shade under sodium light, for counting as red is determined by how it will look in daylight.

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