The author is trying to evoke electroluminescent backlit displays. It's a very specific kind of display technology and it's become fairly uncommon, but for maybe four to ten years it was ubiquitous.

I'm trying to think of an example... the Timex Indiglo watch? A lot of displays with that weird, creepy green or blue glow. Oh, some Palm Pilots and other early handhelds.

I don't actually think e-readers with EL displays are common but some e-readers have a similar color and it's easy to see being confused.