Somewhere (wish I could remember where), I read that the tradition of painting the edging/trim elements of a house a different and contrasting shade from the main structure originated from the idea that it formed an important structural element, because it defined a barrier that unwanted spirits & supernatural forces couldn’t cross. (not unlike the importance of have good downspouts to re-direct other unwanted flows).
Function is one of those concepts that tends to be less and less distinct the closer one looks.
