I want to know the answer to the following question:
What is the meaning of the Latin phrase on Northwestern's seal?
All the background I'm provided with is that "Today, Northwestern's official color is purple, although white is something of an official color as well, being mentioned in both the university's earliest song, Alma Mater (1907) ("Hail to purple, hail to white") and in many university guidelines.". Is that enough to answer the question?