With the exception of yellow, your highlights are too dark for me to read the text easily, so I cannot use them. And there are not enough colors for topical highlighting. Please make them very light, and add more colors: orange, purple, yellow-green, pink, tan. I use a Pentel Arts 8 Color Automatic Pencil which holds eight colors for physical highlighting, use different colors for different topics for ease of quick reference when scanning a book, and need to do the same with Logos books. And underline feature in different colors would also be nice.
