Chris Noessel and Nathan Shedroff demonstrated that in movies depicting computers in the future, the screens are mostly blue.
Some interesting exceptions: 1991's Terminator 2 made red popular, and the Matrix Trilogy made green the in thing for a while. But within a couple of years, we were back to blue. And it's been this way since the 60s.
I think that green usually signifies "old" computers, perhaps? The Matrix was clever in that way.
Forgive me if I'm mistaken, but I'm struck by the thought that the first and third Alien movies (which were British haunted house movies, sort of) used green screens, whereas the second one, Aliens (an American action movie) used blue. Google Images isn't entirely helpful.
Guardians of the Galaxy (above) appears, of course, to be both.