The most useful question to ask initially about color vision is "What is it good for?" The best answer is probably that it allows us to distinguish and identify objects that otherwise would be confused. This emphasis on the properties of objects prompts us to ask whether the characteristics that determine their colors are stable, and how these characteristics might be economically represented in the brain. Most surfaces do have stable attributes, so one might cast the problem of color vision as one of representing the color attributes reliably, despite differences in the conditions under which the objects are viewed.
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