Reminds me of my college note taking practice. I used to take notes with about 3-5 different color pens, and my friends used to be puzzled about it (it sure looks weird to swap between pens often).

I used to reply that the color pens made it easier to keep context such as what teacher said was important, what I found difficult, when in the note I had an "aha!" moment, side comment from me, Q&A asked by student during lecture, or how certain things written down now is related to the point made earlier/later in the lecture/notes.

Text (note) is the content but our (at least mine) attention are not really made for plain text. There's so much more you can play with visual information.