Originally Posted by Dagon
I honestly can't imagine how it would be in bad taste, or any worse than a navy blazer with grey pants aside from tradition.
Not interested in burning you at the stake or saying anything you wear is not in good taste, especially since I have not seen you wear this, but sharing my two cents...
Honestly I think grey trousers just look better in most situations where one is wearing an odd jacket (I think that navy can look good in linen with certain summer odd jackets but that's as far as the exception goes for me). I also think they look better when one is jacketless, though that is much more difficult to articulate.
As for taste or why navy jacket and grey trousers works better than the other way around, tradition is part of it, I think. There's also a practical point. If most men own one odd jacket, it is probably a navy blazer of some sort. If you want to pick a reasonably formal trouser to go with your odd jacket, you're left with grey. Obviously grey is not the only color trouser one can wear with a navy blazer but it is the most formal option that looks good. Grey also goes well with pretty much every other odd jacket option (except grey). I've never wished I had navy trousers to wear with any fall / winter odd jacket (even my grey herringbone odd jacket). I'm sure there are some odd jackets that navy looks okay with, but for me it's an issue of (i) they never look better than grey (outside of some summer outfits) and (ii) they often look worse. Seeing as we get two months or so to wear summer stuff in Chicago (I'm wearing a linen odd jacket today and it's cold outside in mid-June), thoughts of winter heavily influence my wardrobe acquisitions. Clearly we at SF are not most men, but I still think grey is much more versatile.
Most advocates for grey trousers tend to like medium grey (perhaps a bit lighter in summer) and would wear such trousers with a navy blazer, so you get more color contrast. Many think that an odd jacket / odd trouser combination looks best when the jacket is darker. This is achieved nicely with a navy blazer and medium grey flannels. Once you throw on the navy trousers, it's tough to get this contrast look to work. Obviously if you don't care about contrast, you could throw on a dark grey odd jacket as you describe. If it works for you, wear it in good health.