As George Peppard shows in his wardrobe in Breakfast at Tiffany’s, the classic navy blazer and grey trouser combination is perfect to use for those occasions when you do not need the formality of a suit. For me being in a very casual city like Seattle, that usually means it’s ideal for things like wedding events, special dinners out, and the upcoming company holiday parties.

Handy references from Men’s Ex:
The Versatility of the Navy Sportcoat
Navy Sportcoat, Continued

The only trouble with it is, is that you’ll end up wanting to buy an assortment of trousers in different shades of grey… and then maybe in different types of wools…