To kilt in this clan color or that?

[Tobus]

If I come across a tartan I know is a clan tartan I will definitely make a stop here in the future as to gain the knowledge or permission to wear it.

No need to do that. No one here can give you "permission" to wear a clan tartan. You are already free to wear any clan tartan you want. And even if someone here did pretend to give you permission, that wouldn't make a hill of beans to someone who challenged you on it in public.

If it's approval you're looking for, though, the proper person to ask would be the chief of the clan in question. Some chiefs give it freely, some deny it, and some ignore such requests. But wouldn't it be a hoot if you did get written approval from the chief himself, and could throw it in the face of the self-styled tartan police? Oddly enough, usually the bozos who are rude enough to publicly challenge someone's clan affiliation don't even know who their chief is.

DrummerBoy has a great suggestion if you're a Marine. That's one of the tartans you definitely are entitled to wear proudly. But there are also some clan tartans which are also considered universal tartans, due to the fact that they have been worn by military units or for various other reasons. Black Watch (which is actually Campbell) is one. Black Stewart and Royal Stewart are also considered universal, as is Hunting Stewart if I'm not mistaken. So these are actually clan tartans that no one would take amiss if you wore. And a lot of the "plaid" patterns you will find at local fabric stores are variants of these universal tartans. They will look very similar, but seldom exactly like, these tartans.