There's already a question about whether wearing white at a wedding is only taboo in the US, that is not closed, but is this true generally?
Fashion choices are not on topic, but established etiquette is…
Remember that the genesis of this site was a series of failed social proposals with topics as diverse as dating, conflict resolution, and (yes) social etiquette.
This site was the resolution of that shortfall.
So while a question like "is it acceptable to wear white at a wedding" would be on topic (citing well-established conventions of social etiquette), asking how to better match your clothes… is not.
So far "Interpersonal Skills" has generated a lot of questions about being polite, but in my view that only scratches the surface of what this site was meant to be. Where fashion is concerned, if you can carefully navigate that line between establishing social conventions/etiquette versus stuff you just happen to be doing in a social setting, such questions can be acceptable. I know that's not a rock-solid guide to live by, but maybe if I dig up a list of the failed proposal that built this site, it would help enumerate what fields of study may be on and off topic for this site.
Yes, these sorts of questions should be on-topic.
Here's the thing. The first thing that comes to mind when we think about interpersonal skills is talking, but really, there's much more to it than that. Perhaps an example will illustrate.
Imagine you had to interview a job applicant. If he/she comes in dressed in holey jeans and a ratty t-shirt, slouches into the seat, avoids eye-contact, and mumbles something, you already know quite a bit about this person - and they haven't said anything (discernible, anyway).
It's all part of it, from how to dress to make a good impression, to noticing body cues, to actually opening your mouth and talking. If this site covers all interpersonal skills, this site should include all those other things besides just talking - including dress.