analog

Green is commonly used in patient and waiting areas, as is blue, for the calming effect of the color on the psychology of those in the environment. Green is typically held to represent nature, health, good luck, renewal, youth, spring, fertility, etc., and is employed in decorating for that purpose. I've never heard anything of the "reduces eye strain from blood" variety. Yellow is not used that much because it makes people think of sickness, which isn't good for a hospital, nor do they use red for what should be several obvious reasons (makes people on edge, easier to anger, makes them think of blood). Black is obviously out, and plain white is just so stark, they usually toss in some blue or green to liven it up a bit.

It's widely used on medical tables and surgical garb partly because it's a light color, but still fairly low in its own luminosity (unless you use some neon green), so it's not distracting or overwhelming when concentrating on other things, but also because of the soothing, calming property it has on those who have to look at it- and in a hospital, every little thing you can do to reduce fatigue and increase the calm is a good thing.

(and I know this first-hand, from my time volunteering in a hospital, i'm not making it up as I go)