There is no clear requirement for dress, but the unspoken rule is to wear formal clothes. I remember that during the national examination interview in March this year, all our examination rooms were dark. Except for black, no one wore clothes, and both men and women were dressed in formal clothes. Because the interview of civil servants was very strict, the national examination strictly required that you should not disclose or imply your personal information during the interview, otherwise it would be considered cheating. Therefore, if you wear unusual clothes, it may be taken as a hint to the examiner.
So you can wear whatever you like, or you don't have to wear formal clothes, as long as it's not very different, but the style should be generous and decent, and the color should be dark.