Thanks for your guide, I don't mean to undermine it (heh) but here are some good related wiki pages to check out

https://dwarffortresswiki.org/index.php/Color#Color_lists

https://dwarffortresswiki.org/index.php/The_Non-Dwarf%27s_Guide_to_Rock

Any chance you'll add the missing materials to this? Coal is entirely different from everything on here just for 1 example of the missing stuff.

NIce, this is very helpful. To add on to what others are saying about missing materials, I notice you didn't post any ore colors. Malachite in particular I have noticed has a really nice green color to it that I like. Copper too is missing

also Cobalt is missing

i know its not the beautiful blue we had in Classic, but its worth including

should also do glass, theres some neat stuff there

No clay colors..

I linked to this in my guide. Let me know if this is not ok for some reason.

thanks, nice one!

I really love that Chromite color.

The [DISPLAY_COLOR:X:X:X] tag that the materials have refers to the colour palette system that classic DF uses, where instead of getting access to the full RGB spectrum of colour, you designate specific RGB values for each of the 16 colours, you can read more about this on the colour page of the DF wiki.

Also, the hue seems to be determined by the image palettes.png inside the images/ folder, as the palette_default.png references each color to a specific portion of the palettes.png image, where the colours have a gradient from darkest to brightest.