Silly question, but I've always wondered how much men pay attention to this? I'm currently trying to get every bra in every color so they always match, because my friend says that it's raggedy, trashy if a girl doesn't match her undergarments?
Well I guess to be fair color coordinating makes good dress sense. And it speaks about whether someone pays real attention to details. It's kind of like checking a man's socks - you know he has real taste if he cares enough about his appearance to wear coordinated socks. It's like checking how clean someone's bathroom is, or Steve Jobs saying the interior of a mac needs to be as beautiful aesthetically as the outside (even though you can't even open a mac).
In some ways it is a form of deception if you wear a pretty dress on the outside, but don't even care enough to match your underwear.