Not surprising to see no mention of "let the system (and by extension, the user) choose the UI colours if at all possible". It wasn't long ago that you'd set your preferences for colours, fonts, etc. in one place and every application would automatically use them and be consistent. Perfect for colourblind and those who have trouble seeing smaller fonts. UI design has gone backwards.
How would a global preference for colors even work? You can’t just change one color in a palette and expect the design as a whole to still make sense. Imagine a standard thing like a table where you want borders, subtle zebra stripes, focus/selection states, error states, and maybe color coded text for different types of values. Getting that to work at all requires careful coordination of the entire color palette.