Why does the folder color matter? Is it just because that is what you are used to from a specific OS?

Color helps for some people but when making an accessible design you have to account for color blindness and other vision issues. Which means the icon needs enough contrast and can’t rely on just color to convey meaning, unless the icon is paired with a text label that also conveys the meaning the color was trying to convey.

So while I agree that color iconography can be extremely helpful for the average user, unless it is supplemented by other techniques it can make a product completely unusable for a subset of users