Green is better to see by, but red has less of an impact on your night vision especially if you cannot adjust the system brightness.
So I guess it's a choice, is seeing and distinguishing color in the light more important, or is being able to see in the dark after the light. I would guess a green LED would be more disturbing to sleep, at least for me, because psychologically I believe red is "better" and I would have to adjust to the idea of green.
i majored in photojournalism in college and spent lots of time in a traditional darkroom (mid 1970's). Back then with 35mm film, the emulsion was less sensitive to red as long as it wasn't to bright. But some night-vision research i did some time ago talked about aqua or blue/green (507nm wavelenth) being a good compromise for general use at low levels at night. LEDs in this nm are available, usually called "aqua", which also happens to be the color for promoting _good-communication_ in relationships : )