Graduate students, researchers and practitioners are required to stay up-to-date in their area of expertise. This means they regularly read academic papers, white papers, e-books, reports, and other documents that come as PDF.

Having a quick way to switch between colors when highlighting and commenting text (i.e., without relying on the "Comment" menu on the top of the screen) would allow more effective reading.

This could be easily implemented by including a "color" command in the contextual menu that pops up when hovering the mouse on the top of highlighted text (right now it shows "Add comment" and "delete" only).