Don't you just hate losing your place especially for class? Imagine how helpful it would be if each line on a page had its own color so finding your place was quick and easy. Think of all the time and the work hours and studying hours that this would save in the long run. Productivity would skyrocket. So why aren't books ever published that way? I'd go through line by line and do it myself to my books(for class mostly) but I don't have that kind of time.