Just pondering this after seeing the 'how often do you wash your bra' thread.
My knickers and bras match 
I have very small boobs though, so can get away with cheaper bras. Some are really nice sets for 'best' and others are just plainish bras that match plainish knickers of the same colour.
I'll buy one bra and three pairs of knickers that match - had a bit of a spend in M&S yesterday!
I've built it up into too much of a 'thing' I think! No one ever sees it these days but I feel better for them matching, and a bit 'wrong' if I run out - will go braless instead!
But I don't ever wear socks, even in the depths of winter and don't own any - I mean, what would I match them too??
So - are you matchy-matchy or does anything go?