Ok, so messing around with pairing my favourite navy blazer (it's actually somewhere between a blazer and a sport coat - it has shoulder pleats, a little pocket on the back, I got it cut a little longer in the sleeve and it will button closed at the top for cycling... all important to me since I pretty much cycle everywhere) and pairing it with jeans and a tie. I've worn it out with jeans before and received several compliments, but never with a tie.
I went with two knit ties: a sort of mottled grey/deep burgundy and a plain black. I'm not sure which I prefer, if either. The red is a nicer tie, regardless. Also played with loosening the tie and unbuttoning the top button, but it never looks right to me - sloppy rather than casual.
Bonus with scarf/gloves because man, it's cold.
Sorry for the rubbish iPhone photos...