In my impression, librarians usually wear professional suits, but even so, they are very friendly. Personally, I think I can wear some light-colored flat shoes. Most libraries seem to have floor tiles! This way, you won't feel tired after a day's work, and then you won't make a banging sound on the ground because you wear high heels. In fact, I think the most important thing is that wearing light-colored clothes and shoes in summer will make people feel better all day. I hope I can help you. I wish you a happy job!