Review and revise "color" language on wiki.

[benjamin-heasly]

New scene descriptions should use language that distinguishes physical quantities from perceptual phenomena.

https://github.com/DavidBrainard/RenderToolbox3/wiki/Example-Scene-Descriptions

"Color" by itself is ambiguous.

"Spectrum" and "RGB value" are good for physical intensities, reflectances, and reflections.

"Perceived color" is good for perceptual phenomena.

"Apparent" is probably better changed to "perceived" or "inferred".

[benjamin-heasly]

What is a good way to refer to Color Checker grid squares? We use these to choose sampled reflectance spectra. It seems wrong to give them "color" names, since their perceived color would also depend on illumination.

And yet, the squares seem to have obvious names like "red" and "dark gray", which would be meaningful under a wide variety of lighting conditions.

I will split the difference and use phrases like "the red square" or "the square with red-looking reflectance". Hopefully the "-looking" is enough to acknowledge that color is not the same as reflectance.

[benjamin-heasly]

I reviewed all the scene descriptions and updated many of them with clearer language.