Perhaps revisiting what "gimmick" means would help you. Plenty of people use their e-ink readers to look at magazines, comics, news. Plenty of people have a highlighting system. Arguing that color is a "gimmick" is silly considering there are practical applications of color, as we can see around us in the real world. Some of you are seriously living in the weirdest of bubbles.

Biology spent a ton of time adapting and evolving for the ability to see color but sure, it's a gimmick. I guess you should consider syntax highlighting a gimmick in code editors as well? Charts/graphs in textbooks use color as a gimmick, any book that include illustrations/images in color are gimmicks