there actually is an answer to this color conundrum: The highlighted bit of the dress's darker top stripe reads through an eyedropper tool as hex code #806D48, which is a gold-based tone.

The blue, color hex code #4DB1E2, is described as "picton blue ... along with more traditional shades close to silver/gold and space gray. ‌iPhone 15‌ models could have more color options ...