Coming from the Realm associated with the air, Arcans prefer to wear neutral and pastel colours. Roxy accuses them of being colourless, but they just like everything to feel light and airy.
Early on in Fire, Roxy and Avery accuse the Arcans of being prudish, but this is a Helian misconception. The Arcans only cover up because it's so cold! This is particularly true in Jasmine's case - she wears multiple layers to combat the icy climate:
The picture on the beach is how I imagine her waiting for Brae at the start of chapter two.
The cold isn't an issue for the Arcan Protectors though. Their association with the air means that they feel the cold no more than Roxy feels the heat of flames. Devon and Imogen wear things more like this:
And, of course, Arcans love to party. One of the key elements of an Arcan party dress is that it needs to sparkle. At Brae's welcome home party, I imagine Devon and Imogen wearing something like these:
While I think that this would be perfect for Jasmine (with a white blazer on top!)
Sources for all of these images can be found on my Pinterest board (along with lots more pictures!)