Slacks should be fine. Solid neutral color.
If the cold is an issue for you, remember to use layers. (Blouse or shirt) + (cardigan or blazer) + winter coat. It’s important to be comfortable - neither sweating nor shivering.
For an on campus interview that includes a tour, wear practical shoes that you can comfortably walk in (and keep your feet warm). It’s tough to look comfortable when you are in pain from blisters.
That said, I think my kid wore a sweatshirt and leggings to an interview.