Choosing a lip color for your wedding day might seem the least important but its something that really may either tie the look or not that much.
If you never use lip color or if you wear a light neutral shade, having a darker lip for your wedding day is not the best idea. If you really want to try something darker, I would suggest to start wearing darker lip colors right away.
It doesn't have to be a bright color. Try to stick to neutral tones so you start to get used to the color and to the feeling of wearing makeup on your lips (that kind of thing you notice at first but forget forget once you are used to).