Green 110%. I have both. one I got one used when I bought a 1911 (Red) and I ordered a Viridian Laser for my SR9 (Green) I find the red one unless in almost perfect darkness can get "lost" while moving it around. The whole point of a laser is to increase the speed and accuracy of shots in high stress situations, IMHO. So time searching for where your laser is... thats time wasted... Might as well use your sights.
Now the green laser is the exact opposite. Day or night, indoors or outdoors I can see it easily its zeroed right above my front sight in the longest part of my house so its mostly for close range. 30ft roughly. If I'm fighting for my life I wanna have something I can see immediately on my side. Odds are if he can see it there is already a bullet on the way.
It's piece of mind as well. My Girlfriend is becoming an avid shooter but if I am not around and she needs a weapon for self-defense my SR9 is all ready to go 17rds and a green laser, is mine shes not familiar with it, but between her knowledge and the Viridian I am confident she can handle herself.