A few months ago iBooks got an update which allows you to highlight by placing your finger on a word, and after a moment, you just swipe over other words & it highlights using your last style. Then a little window pops up allowing you to quickly change it to an underline or another color.
This has dramatically changed the way I highlight & interact with a book I am reading. I love this new feature & would LOVE this update for the Logos app as well. Maybe after the highlight, have a brief menu pop up that shows the last 5 highlighting styles you have used, along a link or arrow to look at all of them available.