Material changes for all planes. New bug or feature?

Hello all! Was wondering if I could get some help with an issue that seemed to come out of nowhere for me. Have been using planes for reference totally fine for the past however long. Just started a new project, and now all of a sudden I can’t seem to get both my front and side views to show up at the same time. The prominent plane shown here was supposed to be the side view. If both of them have a material, it will be the same material no matter what. Any insight as to if this is either a bug, or if I just accidentally knocked a switch to cause it?