What would be Lessee's argument in winning said suit against TAMU?
I love it when you talk, lawyer.
If TAMU cannot establish ownership of any of the phrases/colors/etc on the billboard, they lose.
There must be infringement (or, at the very least, the possibility of confusion). Those are issues for a judge to decide in the absence of clear ownership of "Aggie Nation", "Whoop!" (whatever the fuck that is), or some other aspect of the content of the billboard.