Thanks raymb1 and Matt Finley.

I have sent an email to PG Support.

I'm using this technique of color coding to help some of my beginner students who are just starting to learn how to read music. It goes along with some software I'm developing to show notes on the guitar fretboard in a color-coded way so that the student can see how the same notes can be played in multiple positions on the guitar. Here's an example (it's still early in development and there are some bugs with the color coding, and the top string isn't working correctly... but you get the idea):