White tie: DS has never needed this. As far as I know, the only events which specify this are one or two of the most expensive May Balls (Trinity? St John's?)
Times may have changed. Trinity says, “The only acceptable attire is traditional Black Tie, White Tie or formal national dress” and St John’s ,”The dress code is strict black tie or national dress. Dresses must be below the knee in length. White tie is not permitted.”
If you search for Trinity May Ball 2023 on Facebook there are hundreds of photos of guests so you can see what they were wearing. (My favourite are the couple in pale blue Japanese National dress, about 27th photo down in Album 2.)
I don’t know about other Cambridge colleges but I understand that those two Balls are indeed the most expensive.