Nowadays they make several colors of lasers,including purple. For me,the green ones are much easier to see.
I have a couple made by Laser Genetics that are used for spotting game. One is a 20mW green that will light up the entire animal (and not just the glow of the eyes) at >500yds. This one is focused at the animal then you target using your normal daylight scope.
The civilian lasers have come a long way in the last 50 years. --- SAWMAN
This laser runs on a cr123. It's a HeNe laser. It's designed for 1 inch ring, has no tuning except to shim the scope ring. It might find a home on a apocalypse build I was fooling with.
You can buy a ring thingy that mounts to your 1" main tube scope,then accepts the 1" laser,light,etc,that is adjustable for R/L and U/D.
I have them for my Laser Genetics lights. They have a 1" barrel. --- SAWMAN