I've been told that an audition is like a job interview. You want to dress up to show that you care and to look nice, but don't come in in a tux or prom dress. Wear something like you would wear to church. I would suggest a dress that looks nice, but color doesn't really matter. Heels vs. Flats- whatever matches the outfit. Patterns vs. Solids- don't think that really makes a difference. Remember- make yourself look good, it never hurts
hope I helped a bit