(See bolder section above.)
This is where we start to veer into the realm of philosophy, perhaps.
Certainly, whilst there is no one, true way that is globally applicable in terms of music, art and so on, it's clear that there are norms (or rules, at the risk of starting a fight!) in regard to such things.
Sure, there are people who push the boundaries - John Cage in music, Damien Hirst in art, to name just a couple - but whilst you'll find some people who will laud them (some because they think that they are genuinely talented, others because they appreciate the iconoclasm) most will think that they are a bit silly.
Sure, some iconoclastic artists/composers/fashion designers and so on were truly talented and groundbreaking but, as apropos pointed out when he referred to Picasso, most of them were well-versed in their field and so knew that they were deliberately traducing traditions in doing what they were doing. If you go to art school, you have to learn about fashion and colour. If you learn an instrument, you have to learn the notes, how to read music, understand rhythm and so on. There are rules that you must learn, before you can then decide to break them.
Fashion, just like art and music, has far fewer rules now than it used to - for the better part of the last century, all of those fields have experienced a softening of formality, the adoption of a more laissez faire approach.
However, whilst most rules about dressing have been softened or disappeared (no brown in town, for example - you'd be hard pressed to find anyone outside SF who knew anything about that) it is a fact that our clothing developed in a particular cultural milieu and it useful to know a bit about those things before you decide to start throwing things on with abandon.
Admittedly, clothing is less of a signifier here than it appears to be in London or in the NE United States, for example, but people still pick up on a well-fitting suit and a well co-ordinated outfit and therefore I think that it does make sense to educate oneself a bit about past and current practices.
I was lucky, in a way, as my father had some "off-the-row" suits that he'd had made for himself in the 1950s or 1960s, and my mother had a good collection of tailored garments from Australian places like Sportscraft from back when they actually made good stuff. They took the time to talk to me about colour combinations, about formal outfits and more outfits and other such things and so by the time I started reading fora like SF and Ask Andy I at least knew a bit already but I guess that there are probably some people around whose parents either did not know or did not care about tailored clothing and so they didn't have that sort of knowledge imparted to them.
BTW JM, my 'here we go again' bit of snark was not directed at you, but appropos.
Apologies for the misunderstanding.