Please hide WN/LN/manga spoilers.
MAL entry, Anilist. The zeroth episode is a spin-off-ish, focusing on Sylphy after the Calamity meeting with Ariel, becoming “silent Fitz”, and struggling with her new situation; as well as the power struggles between Ariel and her brother I-always-forget-his-name for the Asuran throne.
The anime didn’t convey well enough that she was constantly using magic to help try and slow down her fall. As a result, a lot of people are missing the connection of the hair color change with the (over)use of magic.
MT LN Minor Spoilers
Don’t forget the glasses are a magic item which I’m sure will be revealed later in the show.