Attending a wedding is not like high school prom. (There is far less drinking at most weddings.)
It is not mandatory to coordinate your shirt and tie to your date’s dress. It is, however, a nice touch to have a subtle tie-in. For instance, if she is wearing a pink dress, opt for a tie with a touch of pink. Not only will you look good at the wedding, but you’ll also impress your date. She’ll be touched by your attention to detail and obvious fashion savvy when you ask what color of dress she will be wearing. Just be prepared that she might not know for sure until the last minute. In that case, the fact that you asked still gives you bonus points.
Next: What about beach weddings?