Nothing wrong with a good old US of A made denim shirt, worn untucked for slouching around reading, drinking coffee, watching DVDs, listening to Blue Note etc.  I swear, when I first met John Simons, that was exactly how he was wearing his.

For what it's worth, it goes really well with corduroy pants and a Harris tweed jacket.

Hmm dark or a tad faded?
Keep it dark, maybe a touch worn in to look a bit more relaxed and authentic.
But be careful not to step into 'Eagles' territory.

Another of those things that, if I saw one 'Made In The USA' for about a fiver I'd buy it for lounging around in; just as I would a chambray.  I wouldn't necessarily wear it at an Ivy Magic Circle convention and expect Graham Marsh to go "ooh-ah".

thats the kind of thing that became popular after everything got outsourced. with spandex pants, the Girls Ball games mom uniform of the clinton era. old work clothes, as they are generally worked to bits and then discarded, are rare, which is why insane japanese persons pay hundereds of dollars for sweat-stained examples.

navy-issue chambray can probably be found.

I still like the sound of how John Simons wore his denim or chambray.  But perhaps only he could make it work, on the basis that he tended to make everything work.

I'm going to take a chance on a Levi's (from the PWR range).

If I don't like it 'in the flesh' it can go back.

If I do like it, I know from experience that it'll last.