We serve to point people to God. One way that we can do that is be dressing appropriately for our role that day. For those on-platform, what you wear should not distract people, draw attention to yourself, or be inappropriate. And for those off-platform, what you wear should be as distraction-free as possible, so that you can operate quietly and assist in pointing people's attention to God.
Make sure you wear something that makes you feel comfortable, and is true to you! These are guidelines we follow so that we can all work together in our goal of leading people closer to Jesus.