pref night dress - black?

I’m asking for my daughter (she’d kill me if she knew) 😉

The Tech Panhellenic site states that Pref Night Dress does NOT need to be black and the site shows pictures of girls in various colors. But my daughter is active in a Tech PNM/Rushee socia
Media website and she said the girls on the site are all wearing black for Pref Night. Thoughts? She’s afraid of making a fashion faux-pas but can’t ask her friends in Tech houses now due to silent period.

Thank you, ladies! And best of luck to all PNMs...and their mamas!