My future plan for this is to provide color options (via a color picker).
So, for example, I can select some text and apply a light blue highlight, and then select some other text and apply a pink highlight, and so on.
One (sometimes fatal, I think) limitation in the current version is that the highlight is site-wide, so changing the color applies that color change to every highlight on the site.
I mean, I guess it’s useful that the admin can change the highlight color globally, but beyond that it could be more frustrating for end users to see their highlights change color.
@merefield’s approach might be better suited as a starting point.