Are there colors in raw data?

Is there color in raw files? This question comes up over and over. It’s the purpose of this post to provide a more-or-less complete answer to the question, so that I can refer people to it when the topic surfaces in the future. Before we answer the question, we must deal with an issue that Bill Clinton might have described as: “it all depends on what the definition of color is.” Several different things are commonly called color: The physical stimulus. Light has a spectral power distribution. Objects have spectral reflectance or transmittance characteristics. These physical quantities influence color perception, but they are not themselves colors. Color appearance. This is the experienced hue, brightness, colorfulness, saturation, and related perceptual attributes of a stimulus under particular viewing conditions. Color appearance is psychological and depends on much more than the stimulus alone. A colorimetric specification. This represents an equivalence class of stimuli that match…