As I said before, foundations matter. You must understand the standard before you can begin to rebel against it.
That is something I mostly agree with.
But are you suggesting that what is written on that wiki is the standard? If so, why does it lack any references?
To me it seems to try and create rules rather than point them out. Also the information is very weird...
For example the Palettes Applied page..
Painted metals are defined in 3 shades.. since when? What is wrong with 2, 4 or any other number?
I would agree that highly reflective surfaces such as metallic ones show big contrast between the darker (especially if it reflects a dark or shadowed object) and the lighter spots. However the palette you show does not always have big contrast, for example the light teal and medium teal are super close.
Why would you suggest a palette for a specific purpose instead of giving it as an example? (preferably an example showing rendered metal and not just the palette)
No I have not seen these colors at my local art store. Most of these colors are for me very typical screen colors as they can not be recreated without them being a light source. Way too high saturation to look like something I might find on a pencil!
Sorry for the hostility against your wiki project, but it really is not taking a good approach at collecting and displaying information.
This is the 'what would tcaud do' guide, not a pixel art encyclopaedia...